Diopsis Linnaeus, 1775: 5.

Centrioncus Speiser, 1910: 190.

Updated version of the diagnosis by Feijen (1989) for Centrioncidae. Small (4–7 mm), slender flies; head rounded (Fig. 11); eyes not stalked; pedicellus without cleft and in lateral view strongly asymmetrical; funiculus (=first flagellomere) ventrally extended within sagittal plane ~ 1.7× the width of pedicellus, funiculus with a large basal hollow on dorsal half, into which the strongly asymmetrical pedicellar conus is inserted; tripartite pubescent arista; one pair of outer vertical setae and one pair of fronto-orbital setae; lanceolate basiliform prosternum (Fig. 129); supra-alar ridge (carina) present; no pleurotergal spines, three pairs of scutal setae, one pair of scutellar spines with apical setae (Fig. 117), apical setae varying from 20% shorter to 25% longer than spines; costa unbroken, alula present (Figs 1–8), veins CuA+CuP and M4 reaching margin, impression of crossvein bm-cu visible, wings transparent with or without vague spots; incrassate fore femora with double series of ventral tubercles and spinous setae; slender hind femora with distal set of small tubercles; no apical spurs on mid and hind femora; syntergite consisting of tergites 1 and 2; ♀ segment 7 sclerotised basally in complete ring, ♀ sternite 7 transversely divided, ♀ tergite 8 and sternite 8 each consisting of two sclerites; ♂ tergite 6 half as long as tergite 5, main part of ♂ sternite 7 located on left side, very large inverted ♂ sternite 8 (Fig. 136) on both sides fused to sternite 7 which forms a complete ventral band of sclerotisation (Feijen and Feijen 2021: fig. 38); abdominal spiracles 1–6 in membrane, ♀ 7^th spiracles in tergite or not, ♂ left 7^th spiracle in laterally located sternite 7 and ♂ right 7^th spiracle in ventral band of sclerotisation; three (2 + 1) spermathecae; elongate, striated eggs; articulated three-lobed surstylus with tubercles and often spinous setae; subepandrial sclerite with clasper-like ventral lobes and large mesal plate; membranous ♂ cercus; small phallapodeme with posterior two-thirds fused to hypandrium, hypandrial clasper usually present; postgonites and epiphallus present, phallus a short solid structure with a complex distal section; ejaculatory apodeme + sac present, seminal ducts without distinct reticulated transverse structures.

Centrioncus prodiopsis Speiser, 1910: 191, by monotypy.

Various papers from between 1925 and 1983 can refer to the second Centrioncinae genus Teloglabrus or a mixture of the two genera (see Feijen 1983).

Updated version of the diagnosis by Feijen (1983). Centrioncinae with dark maxillary palps; dark section of funiculus limited to around base of arista; central region behind ocellar tubercle usually dark; wing with cell c partly or wholly glabrous, distal section of vein M4 gradually thinner, central wing spot present (Figs 1–8); on average 7–10 spinous setae per fore femur; basal ring of ♀ segment 7 with or without sutures; ♀ tergite 7 well sclerotised and with lateral edges curved under, ♀ sternite 7 split into a broad rectangular anterior plate and a curved or rectangular posterior plate (Figs 14, 104, 133, 148); ♀ 7^th spiracles in tergite or membrane; subanal plate large; epandrium broad and rounded with ratio width/length 1.4–1.5; inner arm of surstylus quite detached from common base of outer and median arms; surstylus in dorsal to dorsolateral position (due to inversion appearing ventrally); outer and median arms with patches of microtrichia on outer side; connection between surstylus and subepandrial clasper short; subepandrial clasper glabrous, without ridges, with 1–3 long setae and 2–8 short setae; inner posterior corner of epandrium without mesad extension for articulation with subepandrial clasper; articulation between subepandrial clasper and cercus via 1–2 small mesad sclerites, the sclerites of both sides linked via a membranous connection; ♂ cercus with distally a broad lateral extension or cercus slender; subepandrial sclerite anteriorly with large lateral extensions, w/l ratio 2.0–2.5; epandrial fold broad and short or epandrial sclerite present; hypandrial clasper with three terminal setae or absent; epiphallus well denticulated, lateral sides of phallophore distally acuminate, phallus rather broad, distal phallic sclerites large and U-shaped; ejaculatory apodeme + sac very large (9.2–16.3% of body length), proximal section of ejaculatory duct at right angles to ejaculatory apodeme.

Figures 1–4. 

Centrioncus, dorsal view of wings 1 ♂, C. aberrans, Timboroa Forest 2 ♀, paratype, C. bururiensis sp. nov., Bururi Nat. Forest 3 ♂ C. bytebieri, Ngangao Forest 4 ♀, paratype, C. copelandi sp. nov., Kasigau Mtn. Scale bars: 0.5 mm.

Figures 5–8. 

Centrioncus, dorsal view of wings 5 ♀, holotype, C. crassifemur sp. nov., N’dalatando 6 ♂, C. decoronotus Njuki-Ini Forest 7 ♂, C. jacobae Mount Soche 8 ♀, C. prodiopsis, Oloitokitok. Scale bars: 0.5 mm.

Centrioncus species are known from Angola, West Africa, and eastern Africa north of the Zambesi (north of 16°S latitude).

Uganda: holotype, ♂, Kilembe, Ruwenzori Range, [0°11'51"N, 30°0'47"E], 1500 m, F.W. Edwards (NHMUK). Paratypes: 1 ♀, 1 ♂, same data as holotype (NHMUK).

Kenya: 8 ♀, 12 ♂, Mount Elgon, nr Elephant Cave (Kitum cave), [1°1'56.84"N, 34°45'28.94"E, 2350 m], 22.iii.1988, H.R. Feijen (RMNH); 1 ♂, Saiwa Swamp, [1°5'43.60"N, 35°6'59.45"E, 1870 m], 23.iii.1988, H.R. Feijen (RMNH); 3 ♂, Rift Valley Province, Timboroa Forest (compt. 9), malaise traps, indigenous Afromontane forest, 00°04.092'S, 35°30.909'E, 2628 m, 14–16.iv.2011, A.H. & M.K. Kirk-Spriggs (BMSA); 1 ♀, Rift Valley Prov., Lake Nakuru N.P., malaise trap, Acacia xanthophloea habitat, 0.35130°S, 36.05795°E, 1796 m, 3-17.iii.2006, R. Copeland (ICIPE); Rwanda: 1 ♂, N. Kivu, Lac Gando, 1°36'S, 29°24'E, 2400 m, 25.xii.1925, H. Schouteden (MRAC); Rwanda & DR Congo [as Zaire]: 2 ♀, x.1993, Thomas Wagner, canopy fogging on specific trees (FBUB) [According to Dr Wagner (pers. comm.), there are two options for the collection site: Rwanda, Cyamudongo, Nyakabuye, 2°34'S, 28°59'E, 1750 m, montane rain forest or DR Congo Irangi, Kivu-Sud, 1°54'S, 28°27'E, 950 m, rain forest. The distance between the two sites is 95 km in a straight line.]. In total 12 ♀ and 19 ♂ were studied.

Centrioncus aberrans can be recognised by its mesally depressed, pruinose frons with two small glossy spots; glossy, blackish brown collar; pruinose, blackish brown scutum; pruinose, brown scutellum with two dark spots; brown scutellar spines; blackish brown pleura, but propleuron, anterior half and posteroventral corner of anepisternum, and dorsal “knob” of anepimeron chestnut brown (Fig. 12); scutellar spine/scutellum ratio: 0.95; apical seta/scutellar spine ratio: 1.13; brown fore femur on distal quarter dark brown on both sides, strongly incrassate (l/w ratio: 2.75) with ~ 35.5 tubercles; medium-sized central wing spot largely in basal quarter of cell r4+5, extending into cells br and bm+dm (Fig. 1); tergites dark brown, thinly pruinose; sternite 4 rectangular (Fig. 13), sternite 5 trapezoidal; sternite 6 a short, broad, trapezoidal sclerite, 1.6× the width of sternites 1–5; female 7^th spiracle half in/half out of tergite; anterior sclerite of female sternite 7 rectangular, w/l ratio: ~ 5.3 (Figs 13, 14); posterior sclerite of female sternite 7 large, weakly sclerotised and rectangular with more sclerotised anterolateral sections; very elongate female cercus with l/w ratio: ~ 5.1; pentagonal subanal plate; smooth spermathecae with some tiny pustules and small dimple surrounded by ridge-like ring; outer and median arms of surstylus broadly joined, with short broad common base (Figs 21–24); outer arm triangular, apically tapering, base twice as wide as apex, rounded apically, with four or five tubercles; median arm broader and longer than outer arm, parallel-sided, with five or six spinous setae; inner arm half the length of median arm, with apophysis; subepandrial clasper (Figs 25–28) with strong basal constriction, rectangular with lateral apical corner a bit extended and rounded, mesal basal corner square; male cercus (Fig. 17) slender, somewhat broadening from base to apex, without distal lateral extension.

Figures 9–12. 

Centrioncus aberrans 9 Mount Elgon, ♀, habitus, lateral view 10–12 Timboroa Forest, ♂ 10 head, dorsal view 11 head, frontal view 12 thorax, lateral view. Arrows indicate glossy spots on frons. Scale bars: 0.5 mm.

Figures 13–15. 

Centrioncus aberrans, Mount Elgon, ♀ 13 abdomen, ventral view 14 sternite 7, ventral view 15 spermathecae. Scale bars: 0.5 mm (13); 0.1 mm (14, 15).

Figures 16–20. 

Centrioncus aberrans, ♂ 16, 20 Timboroa Forest 17, 18 Mount Elgon 19 Lac Gando 16 epandrium with surstyli, posterior view 17 cercus, posterior view 18–20 ejaculatory apodeme. Scale bars: 0.1 mm.

Figures 21–24. 

Centrioncus aberrans, ♂, surstylus, inner view 21 paratype. Uganda. Kilembe 22 Kenya, Mount Elgon 23 Rwanda, Lac Gando 24 Kenya, Timboroa Forest. Scale bar: 0.1 mm.

Figures 25–28. 

Centrioncus aberrans, ♂, subepandrial clasper, outer view 25 paratype, Uganda. Kilembe 26 Kenya, Mount Elgon 27 Rwanda, Lac Gando 28 Kenya, Timboroa Forest. Scale bar: 0.1 mm.

Below, biometrical data are given for the much larger series now studied, as compared to the type series. Additional morphological data, as well as some rectifications, are presented.

Measurements. For the small type series of 1 ♀ and 2 ♂ Feijen (1983) gave for width of head in ♀ 1.12 mm and in ♂ 1.24 and 1.15 mm, body length in ♀ 4.9 mm and in ♂ 5.2 and 5.0 mm, wing length in ♀ 4.4 mm and in ♂ 4.7 and 4.4 mm, and length of scutellar spine in ♀ 0.26 mm and in ♂ 0.27 and 0.26 mm. In Table 2, measurements and other quantitative characters are presented for the much larger series now studied. In this table, data are presented for females and males separately. From this table, the differences between females and males for quantitative characters are marginal. The body length is slightly larger in the male. In Tables 6, 7 the data for females and males are combined, so that large series can be compared with the other Centrioncus species for which large numbers were available. In the other three species for which large series could be measured, the females were, on the average, clearly somewhat larger. The original measurements of the type series of C. aberrans fall well within the ranges as presented in Table 2.

Colour. Most of the specimens now studied were not so dark as those of the type series. These latter three specimens were therefore probably somewhat discoloured, a common tendency in the Centrioncinae (Feijen 1983). The overall colour pattern can be seen in Figs 9–12.

Head. Frons dark brown with anterior edge paler brown (in type-series frons almost uniformly brown), pruinose except two small glossy spots on either side of ocellar tubercle (Figs 10, 11); face, gena and mouthparts pruinose, yellowish brown, palpus blackish; occiput uniformly blackish brown in type series (Feijen 1983), dark brown with more yellowish-brown ventral quarter in additional specimens; length of outer vertical seta 0.36 mm ± 0.00 (n = 17); length of fronto-orbital seta 0.22 mm ± 0.01 (n = 16).

Thorax. Collar glossy blackish brown (Fig. 10); scutum blackish brown, densely pruinose, humeral calli (postpronotal lobes) less pruinose (Figs 9, 12); scutellum pruinose, dark brown in “greasy” specimens but brown with two vague darker spots in other specimens; scutellar spines brown; pleura (Fig. 12) mostly blackish brown, propleuron, anterior half and posteroventral corner of anepisternum and dorsal “knob” of anepimeron chestnut brown (pleura uniformly blackish brown in type series); scutellar spines diverging at angle of ~ 45° (type-series 40°); scutellar spine/scutellum ratio: 0.78 ± 0.01 (n = 18); scutellar spine/body length ratio: 0.056 ± 0.001 (n = 22); apical seta/scutellar spine ratio: 1.13 ± 0.01 (n = 10); scutellar length/scutellar width (at base) ratio: 0.64.

Wing. Subcostal cell not visible in most specimens, visible in one specimen from Rwanda and one specimen of Mt. Elgon; vein CuA+CuP from vein CuP onward slightly curving downward under angle of 30° to wing margin (Fig. 1); central wing spot distinct, medium-sized, largely in basal quarter of cell r4+5, extending into cells br and bm+dm; vague infuscation along vein M4; cell cua in between triangular and rectangular (Fig. 1).

Legs. Fore femur (Fig. 9) yellowish with distal quarter on both sides dark brown (only Lac Gando specimen on inner side with distinct brown stripe on distal third); fore femur strongly incrassate, l/w ratio: 2.75 ± 0.01 (n = 22), two rows of spinous setae on distal two-thirds with 9.0 ± 0.1 setae (n = 45), inner row with 4.9 ± 0.0 setae and outer row with 4.1 ± 0.0 setae, two rows of tubercles on distal three-quarters with 35.4 ± 0.5 tubercles (n = 42), inner row with 17.2 ± 0.2 tubercles and outer row with 18.2 ± 0.3 tubercles; hind femur distally with 6.5 ± 0.2 (n = 46) tubercles in single row but in two specimens one tubercle placed in second row; setal formula (sensu Feijen 1983) of 4.1, 4.9, 18.2, 17.2, 6.5 vs. formula of type-series: 4.0, 5.2, 16.8, 15.2, 6.5.

Preabdomen. Dorsally dark brown, thinly pruinose; posterolateral corners of tergite 2 paler brown; sternites 1–6 brown, thinly pruinose, sternite 2 more glossy; sternite 1 rectangular, constricted on meson (Fig. 13); sternite 2 anteriorly with mesally narrow, strongly sclerotised intersternite 1–2, laterally with thin extensions connected to main sternite 2; sternites 3 and 4 rectangular (Fig. 13), sternite 5 trapezoidal, broadening posteriorly; sternite 6 short, broad, trapezoidal, broadening posteriorly, ~ 1.6× width of sternites 1–5.

Female postabdomen. Seventh spiracle half in/half out of tergite or touching tergite (Fig. 14); anterior sclerite of sternite 7 with w/l ratio: ~ 5.3 (5.2–5.4); flies from Mt Elgon with weakly sclerotised rectangular plate (with rounded anterior corners) of posterior sclerite of sternite 7, as in female paratype with two large more sclerotised sections joined anteromesally (Figs 13, 14); spermathecae as in paratype (spherical with small apical dimple with small ring); junction of ducts of paired spermathecae T-shaped (Figs 13, 15).

Male postabdomen. Epandrium yellowish brown, darker brown anteriorly (Fig. 16) (uniformly brown in type series); qualitative characters conform with original description; surstylus of paratype ♂ (Fig. 21) identical to specimens from Mt Elgon, Lac Gando and Timboroa forest (Figs 22–24); narrow cercus, without apical lateral extension, length/greatest width ratio: 2.6 (Fig. 17, Table 8); subepandrial clasper of males from three localities (Figs 26–28) similar to paratype (Fig. 25); epandrial fold (periandrial fold sensu Feijen (1983)) consists of one single piece, with inner section of fold not detached to form epandrial sclerite (stated as detached in the original description); quantitative characters agree well; outer arm of surstylus with 4–5 tubercles in type-series and specimens from Kenya and Rwanda (Figs 21–24); median arm of surstylus with 6 stout spinous setae in type series, and only 5 spinous setae in specimens from Mount Elgon, Timboroa, and Rwanda (Figs 21–24); basal setulae on outer arm and setulae on inner arm distinctly larger in Kenya specimens (Figs 22, 24); ejaculatory apodeme + sac in all four males (from Rwanda, Mount Elgon, and Timboroa Forest) (Figs 18–20, Table 9) very large (9.3, 10.1, 10.1 and 11.2% of body length, respectively) (shorter in paratype).

In the map of Eastern Africa (Fig. 29), the collection localities for C. aberrans are indicated. The eastern branch of the Great Rift Valley appears to form a barrier between the populations of C. aberrans and C. decoronotus. The two females collected in DR Congo/Rwanda are not indicated on the map. These two flies were collected by canopy fogging of individual trees. The methodology used for this fogging is explained in Wagner (2000, 2001). Funnel-shaped sheets were attached to the trees at waist height for collecting the dropping insects. Dr Wagner (pers. comm.) explained that “The lowest branches hit by the fog were about 3 metres [high] and it reaches usually ≤ 10 m.”

Figure 29. 

Distribution map of the seven Eastern African Centrioncus species.

Feijen (1983) indicated the habitat for Centrioncus and Teloglabrus was low shrubs and herbaceous plants. We collected the flies at heights of ~ 20–60 cm from ground level. The results of the canopy fogging trials possibly indicate that Centrioncus flies might also occur at higher levels in the trees, though disturbance of the flies or descending insecticide might form alternative explanations. Nothing is known about where oviposition occurs and larval feeding, so the possibility of breeding in the tree canopy cannot be excluded. The flies of C. aberrans from Timboroa Forest in Kenya were collected in a malaise trap. The height at which these flies were trapped is more in line with the habitat indicated by Feijen (1983). The Timboroa habitat is illustrated in Fig. 30.

Figure 30. 

Centrioncus aberrans, Kenya, Timboroa Forest, collection site, 2011. Photograph by A.H. Kirk-Spriggs.

Given the unusually large range of distribution of this Centrioncus species, special care was taken to examine and compare defining characters such as surstylus, subepandrial clasper, male cercus and female sternite 7 for flies from the regions involved: western Uganda, western Rwanda, western and more central Kenya (Fig. 29). Comparisons of surstyli (Figs 21–24) and subepandrial claspers (Figs 25–28) lead to the conclusion that they are largely similar. For the surstyli, the general shape, number of tubercles and number of spinous setae correspond well. Also, the very specific female sternite 7 (Figs 13, 14) is very similar to the female paratype. The subepandrial clasper of the paratype (Fig. 25) appears less broad, but this is caused by it being slightly tilted to the right during the preparation. While comparing the shapes of the surstyli, care must be taken to present these three-dimensional structures as much as possible in the same plane. In the drawing of the surstylus of the paratype male (Fig. 21), the median arm is slightly tilted upward, so this arm appears somewhat shorter. Likewise, the inner arm of the surstylus in the Lac Gando specimen (Fig. 23) is somewhat tilted and so appears a bit different. In addition, small differences in shape of the three arms and size of setulae are observed and it could be argued that this species is in a very early phase of allopatric speciation. However, if one looks at the major differences for these defining characters between the Centrioncus species (Figs 51, 69, 88, 122, 138, 150; Feijen 1983), the conclusion can be drawn that all specimens examined across the large distribution range belong to one species, C. aberrans.

South Sudan, holotype, ♀, Nagichot, [4°16'37.99"N, 33°33'34.99"E, 1980 m], D.J. Lewis (NHMUK) (not examined, but notes and pencil drawings for Feijen (1983) were used).

(after Feijen 1983). Centrioncus angusticercus can be recognised by its pruinose, mesally slightly depressed frons with two glossy spots; dark brown collar; blackish brown scutum; blackish brown scutellum with pale brown lateral sides and spines; pleura blackish brown except for brown propleuron and anterior anepisternum; apical seta/scutellar spine ratio: > 1.0; pale brown fore femur with distal third on inner side dark brown and small dark spot apically on outer side, with 36 tubercles; small round central wing spot (Fig. 31) around junction of crossvein r-m and vein M1 in tip of cell br and base of cell r4+5 slightly extending into cell bm+dm; tergites blackish brown, apical edges paler; female 7^th spiracle just in tergite; anterior sclerite of female sternite 7 rectangular, w/l ratio: ~ 4.4; posterior sclerite of female sternite 7 consisting of well-sclerotised trapezoidal anterior plate and two weakly sclerotised posterolateral extensions (Fig. 32), anterior edge of anterior plate parallel to its posterior edge, short lateral sides straight, slightly broadening posteriorly, posterior side concave, weakly sclerotised posterolateral extensions irregularly shaped and posteriorly with 6–8 setulae; very elongate female cercus with l/w ratio: 5.4 (Table 8); pentagonal subanal plate; smooth round spermathecae with some tiny pustules and small dimple surrounded by ridge-like ring.

Figures 31, 32. 

Centrioncus angusticercus, ♀, holotype, Nagichot, South Sudan 31 wing, dorsal view 32 sternite 7, ventral view. Scale bars: 0.5 mm (31); 0.1 mm (32). Both drawings were processed based on original pencil drawings from Feijen (1983: figs 13, 27).

Wing. Small, rounded, elongate central wing spot (Fig. 31) around junction of crossvein r-m and vein M1, in posterior part of tip of cell br and posterior part of base of cell r4+5 to halfway to crossvein dm-m, slightly extending into cell bm+dm; very vague infuscation along vein M4 between cell cua and crossvein dm-m; vein CuA+CuP from vein CuP onward extending under an angle of 25° to wing margin in straight line; vein M4 continuing distally from crossvein dm-m in straight line to wing margin.

Female postabdomen. Anterior sclerite of sternite 7 rectangular, tapering posteriorly, lateral sides convex, w/l ratio: ~ 4.4 (Fig. 32, Table 8); posterior sclerite of sternite 7 consisting of well-sclerotised trapezoidal anterior plate and two weakly sclerotised posterolateral extensions (Fig. 32); anterior edge of anterior plate parallel to posterior edge of anterior sclerite, short lateral sides straight, slightly expanded posteriorly, posterior edge concave; weakly sclerotised posterolateral extensions irregularly shaped and posteriorly with 3–4 pairs of setulae; very elongate female cercus with l/w ratio: 5.4 (Table 8).

In the Shillito archive (now in NHMUK), a letter was found written on 22 January 1950 by D.J. Lewis, the collector of the holotype, and addressed to J.F. Shillito. It provided information on the collecting locality of the single known specimen: “The Diopsid, Centrioncus prodiopsis Speiser, was taken at an altitude of about 1980 metres among vegetation near a small stream in a patch of forest. Nagichot is on the Didinga Hills, one of the many isolated ranges, and may be considered as part of the Eastern and Southern zoogeographical Province ...” The type locality is shown on the map for Eastern Africa (Fig. 29).

Feijen (1983) described the posterior sclerite of sternite 7 as “very roughly U-shaped with eight hairs, anterior edge parallel to posterior edge of sternum 7, anterior section well sclerotized, but arms of the U connecting to posterior hairs of sclerite weakly sclerotized.” However, the view that this sclerite can be described as “U-shaped” is now rejected (compare Fig. 32 vs. Figs 43, 62, 82, 119, 133, 148). Centrioncus angusticercus is now placed outside the group of Centrioncus with a U-shaped sclerite. Instead, it is considered as closer to the other Centrioncus without a U-shaped sclerite: C. aberrans and C. crassifemur sp. nov. Other similarities like l/w ratio of ♀ cercus and w/l ratio of ♀ anterior sternite 7 also support this group. For a confirmation of this relationship, the discovery of the male sex and study of the male genitalia of C. angusticercus and C. crassifemur sp. nov. and molecular analyses will be required.

Burundi, holotype, ♀, Bururi Nat. Forest, 3°55'49"S, 29°37'1"E, 1955 m, 7–21.ix.2010, R. Copeland, malaise trap, indigenous forest near stream (NMKE). Paratypes: 1 ♀, 1 ♂, same data as holotype (ICIPE, RMNH).

Centrioncus bururiensis sp. nov. can be recognised by the mesally slightly depressed, uniformly pruinose frons; mainly glossy collar; pruinose blackish brown scutum; pruinose, blackish brown scutellum with brown spines; pleura blackish brown with ventral edge of proepimeron, dorsal third of anepisternum, posterior quarter of anepimeron, and greater ampulla brown; scutellar spine/scutellum ratio: 0.8–0.9; apical seta/scutellar spine ratio: 0.94–1.18; pale brown, strongly incrassate fore femur 1 (l/w ratio: 2.63–2.93) with ~ 38.5 tubercles, dark apical third on mesal side; small central brownish wing spot around crossvein r-m in distal tip of cell br and basal quarter of cell r4+5, somewhat extending into cell bm+dm (Fig. 2); tergites blackish brown, thinly pruinose; sternites 4 and 5 rectangular with each a pair of small, heavily sclerotised areas basally; sternite 6 short, almost as broad as segment, laterally tapering; female 7^th spiracle in membrane; anterior sclerite of female sternite 7 rectangular, w/l ratio: ~ 2.6 (Figs 42, 43); posterior sclerite of female sternite 7 broad, strongly curved, U-shaped, well sclerotised (Figs 42, 43), posterolateral apices tapering; elongate female cercus with l/w ratio: ~ 4.5; subanal plate pentagonal, laterally rounded and apically tapering into short extension; spermathecae heavily sclerotised, smooth, flattened (Fig. 49), rounded in cross section, with small apical dimple; outer and median arms of surstylus broadly joined, with short broad common base (Fig. 51); outer arm triangular, apically 4 tubercles; median arm very broad, parallel-sided, apically 11 stout, spinous setae; inner arm half the length of median arm, with apophysis; subepandrial clasper (Fig. 53) with long strong basal constriction, extended towards meson, rectangular with apical corners square, mesal basal corner rounded; male cercus (Fig. 54) slender, distinctly broadening in apical third but without distal lateral extension.

Measurements. Body length ♀ 5.8, 5.8 mm, ♂ 4.6 mm, width of head ♀ 1.28, 1.27 mm, ♂ 1.07 mm, wing length ♀ 5.3, 5.2 mm, ♂ 4.1 mm, length of scutellar spine ♀ 0.39, 0.36 mm, ♂ 0.27 mm.

Head. Frons slightly depressed mesally (Fig. 34), dark brown but anterolateral margins pale brown, uniformly thinly pruinose; posterior side of head dark brown with paler brown ventral margin (Fig. 36), pruinose especially posterior to ocellar tubercle and near eye margins; face yellowish brown, thinly pruinose but densely pruinose along eye margins (Figs 34, 35); antenna yellowish brown but dorsal edge of funiculus darker (Figs 34–36, 38); maxillary palpus dark (Figs 34, 35); outer vertical seta in ♀ 0.41 mm and in ♂ 0.31 mm, fronto-orbital setae in ♀ 0.29 mm and in ♂ 0.18 mm (Figs 34, 36).

Figures 33–36. 

Centrioncus bururiensis sp. nov., Bururi Nat. Forest 33 ♂, paratype, habitus, dorsolateral view 34–36 ♀, paratype 34 head, anterolateral view 35 head, basiliform prosternum, ventral view 36 head, thorax, fore femora, lateral view. Scale bars: 0.5 mm.

Thorax. Collar glossy dark brown, posterior and lateral edges pruinose; scutum blackish brown and pruinose (Figs 33, 36), tiny pale spot around base of intra-alar seta, humeral callus brown and less pruinose; scutellum dark brown, pruinose, scutellar spines brown (Figs 33, 36); pleura blackish brown with ventral edge of proepimeron, dorsal third of anepisternum, posterior quarter of anepimeron, and greater ampulla brown (Fig. 36), but, like in all Centrioncus, paler sections can also turn dark (Fig. 33); pleura mainly pruinose, glossy sections include ventral edge of anepisternum and anterior spot on katepisternum (Fig. 36); posterior notopleural seta, supra-alar and infra-alar setae present, infra-alar seta longest, followed by posterior notopleural seta, supra-alar seta on inconspicuous carina; basiliform prosternum lanceolate and sharply pointed anteriorly (Fig. 35); scutal length/scutal width ratio: 1.0 in ♀ and ♂; scutellum sticking up at an angle of just over 20° from body axis; scutellar spines almost aligned with dorsal plane of scutellum (Fig. 36), diverging at angle of ~ 50°; scutellar spine/scutellum ratio: 0.9 in ♀, 0.8 in ♂; scutellar spine/length of body ratio: 0.06–0.07 in ♀, 0.06 in ♂; apical seta/scutellar spine ratio: 0.94 in ♀, 1.18 in ♂, scutellar length/scutellar width (at base) ratio: ~ 0.70.

Wing. Almost transparent but slightly tinged; small, central brownish spot around crossvein r-m in distal tip of cell br and basal quarter of cell r4+5, vaguely extending into cell bm+dm (Fig. 2); some vague infuscation around vein M4 proximally of crossvein dm-m; glabrous basal areas only include cells bc and c and basal third of cell br; crossvein h distinct; cell sc almost closed; vein CuA+CuP from vein CuP onward extending under angle of 30° to wing margin in almost straight line (Fig. 2); vein M4 continuing distal of crossvein dm-m very slightly turning downwards towards wing margin; cell cua triangular; alula distinct; crossvein bm-m hardly indicated.

Legs. Coxa 1 and trochanter 1 whitish, thinly pruinose (Figs 35, 36); femur 1 glossy, yellowish brown with dark brown spot on apical third of inner side, darker in ♂ and extending to outer side (Figs 33, 36, 39); tibia 1 dark brown, pruinose; metatarsus 1 yellowish, other tarsal segments whitish; mid and hind legs pale yellowish; femur 2 with pale brownish apex; outer apical quarter of femur 3 with brown spot (Fig. 37); femur 1 strongly incrassate in ♀ and ♂ (Figs 33, 36, 39, 40), l/w ratio in ♀: 2.87, 2.93 and in ♂: 2.63, inner rows of spinous setae (Figs 39, 40) with 4.8 setae (n = 6, range 4–5), outer rows with 4.0 setae (n = 6, range 3–5), inner rows of tubercles with 18.3 tubercles (n = 6, range 17–20), outer rows with 20.2 tubercles (n = 6, range 18–23); femur 3 (Fig. 37) with 6.8 distal tubercles (n = 4, range 5–8); setal formula 4.0, 4.8, 20.2, 18.3, 6.8; no apical spurs on femora 2 and 3.

Figures 37–40. 

Centrioncus bururiensis sp. nov., Bururi Nat. Forest 37, 39, 40 ♀, holotype 38 ♀ paratype 37 hind femur, outer view 38 antenna, lateral view 39 fore femur, inner view 40 fore femur, ventral view. Scale bars: 0.2 mm.

Preabdomen. Tergites blackish brown, very thinly pruinose; sternites 1–5 yellowish brown, sternites 1–3 glossy and clothed with some setulae (Fig. 41), sternites 4–5 thinly pruinose, with some setulae; sternite 1 very short, constricted medially; sternite 2 anteriorly with small more sclerotised sclerite (plesiomorphic equivalent of intersternite 1–2 found in most Diopsidae), laterally thinly connected to main sternite, separated from main sclerite by short, non-sclerotised “gap” (Fig. 41); sternites 2–5 rectangular, slender, more or less equal in width (Fig. 41), sternite 3 20% shorter than sternite 2, sternite 4 only half length of sternite 2 and sternite 5 only one-third length of sternite 2; sternites 4 and 5 both with pair of small, heavily sclerotised sections anteriorly (Fig. 41); sternite 6 short and broad, laterally tapering, almost as broad as segment, 1.6× as wide as sternites 1–5 (Fig. 42).

Figures 41–43. 

Centrioncus bururiensis sp. nov., Bururi Nat. Forest 41, 43 ♀, paratype 42 ♀, holotype 41 sternites 1–5, ventral view 42, 43 sternite 7, ventral view. Scale bars: 0.5 mm (41); 0.1 mm (42, 43).

Female postabdomen. Tergite 7 (Figs 42, 44) brown, with large mesal gap posteriorly, lateral edges hardly curved under ventrally; suture in basal ring of segment 7 hardly visible; 7^th spiracle in membrane (Fig. 43); anterior sclerite of sternite 7 rectangular, slightly tapering posteriorly (Figs 42, 43), w/l ratio: ~ 2.6 (Table 8), glossy brown, with ~ 16 setulae and some microtrichia only on posterior edge; posterior sclerite of sternite 7 broad, strongly curved U-shaped (Figs 42, 43), almost forming semicircle, posterolateral apices tapering, well sclerotised, clothed in microtrichia and with one apical setula; tergite 8 consisting of two oblong plates, well separated on meson (Fig. 45); sternite 8 consisting of two oblong plates; tergite 10 (Fig. 45) somewhat onion-shaped, extending posteriorly between cerci, clothed in microtrichia and a few setulae; cercus elongate, somewhat tapering posteriorly (Fig. 44; cut off in paratype, Fig. 45), l/w ratio: ~ 4.5; subanal plate (Fig. 46) somewhat pentagonal, laterally rounded and apically tapering into short extension, clothed in microtrichia except anterior edge, with ~ 12 setulae especially along posterior edge; spermathecae heavily sclerotised, smooth, flattened (Fig. 49), round in cross section, with small apical dimple; junction of ducts of paired spermathecae V-shaped (Fig. 49).

Figures 44–49. 

Centrioncus bururiensis sp. nov., Bururi Nat. Forest 44 ♀, holotype 45–49, ♀, paratype 44 tergite 7, 8, 10, cerci, dorsal view (setulae not shown) 45 tergite 8, 10, basal cerci, dorsal view 46 subanal plate, ventral view 47 egg 48 egg, detail 49 spermathecae. Scale bars: 0.2 mm (44, 47); 0.1 mm (45, 46, 48, 49).

Male postabdomen. Tergite 6, sternite 8 and epandrium more brownish than blackish brown tergites 1–5; sternite 6 rectangular, almost as broad as tergite 6; epandrium broad and rounded (Fig. 50) with w/l ratio: 1.31, dark brown but paler brown along inner edges, clothed in microtrichia and with ~ 6 small setulae; surstylus in outer view (Fig. 50) not deeply bifurcated, with central patch of microtrichia on outer side; outer and median arms broadly joined, with short broad common base (Fig. 51); outer arm almost triangular, tapering apically, not constricted at base, with four apical, closely joined tubercles, basally to centrally with seven setulae on inner side and a few small setulae along posterior edge; median arm very broad, parallel-sided, with apically 11 stout, dark, spinous setae, some small pale setulae and two long setulae (Figs 50, 51); inner arm linked to base of other arms, half-length of median arm, tapering apically, with one apophysis and five strong setulae; subepandrial clasper (Fig. 53) with long strong basal constriction, extended mesally, rectangular with apical corners almost square and mesal basal corner rounded, glabrous; cercus (Fig. 54) slender, distinctly broadening in apical third, without distal lateral extension, clothed in microtrichia, with short setulae mainly along mesal edge, length/greatest width ratio: 2.4 (Table 8); phallapodeme short; ejaculatory apodeme + sac (Fig. 52) very large, 10.4% of body length (Table 9), ejaculatory apodeme club-shaped, basally slender.

Figures 50–54. 

Centrioncus bururiensis sp. nov., ♂, paratype, Bururi Nat. Forest 50 epandrium, cerci, surstyli, posterior view 51 surstylus, inner view 52 ejaculatory apodeme + sac 53 subepandrial clasper, posterior view 54 cercus, posterior view. Scale bars: 0.1 mm.

Egg. ♀ paratype contained 45 developing and developed eggs in abdomen. The eggs (Figs 47, 48) measured ≤ 1.10 mm in length, with slightly elevated longitudinal ridges spanning from anterior pole to posterior pole with fine, nearly hexagonal microstructure between ridges (Fig. 48).

The new species is only known from the Bururi National Forest in Burundi. It was collected at an altitude of 1955 m. This small Afromontane Forest is relatively isolated from other similar forests. The type locality is shown on the map for Eastern Africa (Fig. 29).

The specific epithet of C. bururiensis sp. nov. refers to the place of origin for the holotype, the Bururi Forest in Burundi.

While cursorily examining the three flies of the Bururi Forest, the male fly appeared to be Centrioncus aberrans, given the apparently similar shapes of surstyli and cerci. However, the females with their clearly visible curved posterior sclerite of sternite 7 (Figs 42, 43) did not belong to the C. aberrans species-group. This led to the initial assumption that this might be the first case of two Centrioncus species occurring sympatrically. However, closer examination of the male genitalia revealed distinct differences with those of C. aberrans. The female is also different from other described Centrioncus with the characteristic sternites 4, 5, and 7 and the spermathecae. The subanal plate of C. bururiensis sp. nov. is more like those of C. decoronotus and C. prodiopsis, not like C. aberrans (compare Fig. 46 vs. Feijen 1983: figs 49–51). The w/l ratio of the anterior female sternite 7 is like the ones for C. decellei, C. bytebieri and C. prodiopsis, certainly not like the one for C. aberrans (Table 8), while the shape of posterior sclerite of sternite 7 is more like the one for C. decoronotus and certainly not like C. prodiopsis or C. bytebieri (compare Figs 119, 148, 62 vs. De Meyer 2004: fig. 6).

It remains puzzling that the male genitalia of Centrioncus bururiensis sp. nov. indicates a possible relationship with C. aberrans, while the female genitalia contradicts such a relationship. Analyses, including molecular analysis, of a series of fresh material are required to resolve this issue. The number of 45 eggs found in a paratype was quite high. Feijen (1983) found in various Centrioncus and Teloglabrus species > 20 developing and developed eggs and stated that a fecundity of between 25 and 50 eggs seemed likely. The gravid female paratype was collected in September, coinciding with the start of the short rains in Burundi.

Kenya, holotype, ♂, Ngangao Forest, Taita Hills [3°21'38"S, 38°20'29"E, 1800 m], M. De Meyer (NMKE). Paratypes: 8 ♀ (1 ♀ as “allotype”), 7 ♂, same data as holotype; 8 ♀, 10 ♂, Chawia Forest, Taita Hills [3°28'56"S, 38°20'25"E]; 5 ♀, 6 ♂, Yale Forest, Taita Hills [3°24'7"S, 38°19'36"E]; 5 ♀, 2 ♂, Mbololo Forest, Taita Hills [3°19'36"S, 38°27'3"E]. All paratypes collected by M. De Meyer at altitudes of 1400–1800 m, allotype NMKE, 2 paratypes NHMUK, 2 paratypes NMSA, 46 paratypes MRAC.

Kenya: 2 ♀, Coastal Prov., Taita Hills, Mbololo Forest, malaise trap 3°20.00'S, 38°26.85'E, 1550 m, 29.iii–6.iv.1999, Taita biodiversity project (ICIPE); 1 ♀, 1 ♂, Coastal Prov., Taita Hills, Fururu Forest, malaise trap, 3°25.78'S, 38°20.30'E, 1680 m, 23–29.i.1999, Taita biodiversity project, (ICIPE); 1 ♀, Coastal Prov., Taita Hills, Chawia Forest, malaise trap next to small forest pond, 3.47908°S, 38.34162°E, 1614 m, 9–23.i.2012, R. Copeland (ICIPE); 1 ♀, 4 ♂, Coastal Prov., Taita Hills, Vuria Forest, malaise trap, edge indigenous forest, 3.41428°S, 38.29178°E, 2162 m, 1 ♂ 12–6.vi.2011, 1 ♀ 11–25.i.2012, 1 ♂ 13–27.v.2012, 1 ♂ 25.vii–8.viii.2012, 1 ♂ 8–22.viii.2012, R. Copeland (ICIPE); 5 ♀, 1 ♂, Coastal Prov., Taita Hills, Ngangao Forest, malaise trap, indigenous forest, 3.36100°S, 38.34186°E, 1848 m, 1 ♀ 30.x–13.xi.2011, 2 ♀ 24.i–7.ii-2012, 1 ♀ 8–22.ii.2012, 1 ♂ 19.iv–3.v.2012, 1 ♀ 27.v–10.vi.2012, R. Copeland (ICIPE). In total 10 ♀ and 6 ♂ were studied.

Centrioncus bytebieri can be recognised by the pruinose frons with glossy spots; glossy collar; pruinose blackish brown scutum; scutellum blackish brown with brown lateral sides; scutellar spines brown; pleura blackish brown with largely brown proepisternum and strikingly brown central area formed by anepisternum, anepimeron and greater ampulla (Figs 55, 57); scutellar spine/scutellum ratio: 0.95; apical seta/scutellar spine ratio: 1.14; pale brown, incrassate fore femur (l/w ratio: ~ 3.30) with ~ 33 tubercles, broad brown stripe on distal half; small, central brownish wing spot around crossvein r-m in distal tip of cell br and basal fifth of cell r4+5, somewhat extending into cell bm+dm (Figs 3, 55); tergites blackish brown, syntergite with small pale spots in posterolateral corners (Fig. 60), tergite 3 with pale posterior band; sternite 4 trapezoidal; sternite 5 rectangular; sternite 6 short and broad; female 7^th spiracle in tergite; anterior sclerite of female sternite 7 rectangular, w/l ratio: ~ 2.6 (Figs 61, 62); posterior sclerite of female sternite 7 somewhat U-shaped, with posterolateral extensions almost extending to posterior corners of tergite 7, lateral sections outwardly curved (Figs 61, 62); female cercus rather broad with l/w ratio: 2.3; subanal plate short, broad, triangular with rounded apex (Fig. 63); spermathecae well-sclerotised, smooth, rounded with shallow apical dimple; common base of outer and median arm of surstylus long, slender; outer arm of surstylus basally constricted, apically > 1.5× width at base, with 6–9 tubercles (Figs 68–70); median arm slender, longer than outer arm, with 3–6 spinous setae; inner arm of surstylus two-thirds length of median arm, with apophysis; subepandrial clasper (Figs 69, 70) trapezoidal, basally narrower, mesal apical corner rounded, lateral apical corner pointed; male cercus (Fig. 71) with broad lateral extension, slightly concave apically.

Figures 55–60. 

Centrioncus bytebieri, ♀ 55, 57–60 Ngangao Forest 56 Vuria Forest 55 habitus, lateral view 56 head, frontolateral view 57 thorax, lateral view 58 fore femora, ventral view 59 hind femur, inner view 60 abdomen, dorsal view. Scale bars: 0.5 mm.

Below, biometrical data are presented for the series now studied, and compared to the type series. Additional morphological data, as well as a few rectifications, are presented.

Measurements. For the type series of 26 ♀ and 26 ♂, De Meyer (2004) stated body length 5.59 mm (4.95–6.80) and wing length 4.83 mm (4.55–5.10). In Table 3, measurements and other quantitative characters are presented for the series now studied. In this table, data are presented for females and males separately. The table shows that differences between females and males for quantitative characters are small. The body length and various other measurements are slightly larger in females. In Table 6, the data for females and males are combined, so that large series can be compared with other Centrioncus species for which large numbers were available. The original measurements of the type series agree well with the means and ranges as presented in the tables: body length 5.55 mm ± 0.09 vs. 5.59 mm and wing length 5.04 mm ± 0.06 vs. 4.83 mm. The measurements confirm C. bytebieri as one of the larger Centrioncus, together with possibly C. angusticercus and C. bururiensis sp. nov. (based on measurements presented in this paper (Tables 6, 7), and Feijen (1983)).

Colour. De Meyer (2004) gave a fine description of the colouration. Characteristic colouration of pleura in prime specimens should be stressed (Figs 55, 57). Yellowish-brown sections include proepisternum, proepimeron, anepimeron with greater ampulla, posterodorsal corner of katepisternum and anterior spot on meron.

Head. Frons (Fig. 56) thinly pruinose, laterally densely pruinose, with glossy spots (reduced in some specimens) laterally of ocellar tubercle; length of outer vertical seta 0.38 mm ± 0.01 (n = 16), length of fronto-orbital seta 0.28 mm ± 0.00 (n = 16) (see Tables 6, 7).

Thorax. Scutum densely pruinose, humeral calli and lateral sections behind intrascutal suture thinly pruinose, almost glossy; proepisternum with dorsal third blackish, ventral area brown; anepisternum, anepimeron and greater ampulla brown, leading to striking central brown area on pleura (Figs 55, 57); posterodorsal section of katepisternum brown, other pleura blackish; glossy sections on pleura include ventral edge of anepisternum and large central spot on katepisternum (Fig. 57); scutellar spine/scutellum ratio: 0.95 ± 0.01 (n = 16, Table 6); scutellar spine/body length ratio: 0.064 ± 0.001 (n = 16); apical seta/scutellar spine ratio: 1.14 ± 0.02 (n = 12); scutellar length/scutellar width (at base) ratio: 0.66.

Wing. Central brownish spot around crossvein r-m in distal tip of cell br and basal fifth of cell r4+5, somewhat extending into cell bm+dm (Figs 3, 55); some infuscation around vein M4 proximal to crossvein dm-m; vein CuA+CuP from vein CuP onward extending under angle of 30° to wing margin in almost straight line (Fig. 3); cell cua triangular; vein M4 continuing distal of crossvein dm-m, gradually thinning, very slightly turned downwards towards wing margin.

Legs. Femur 1 on almost distal half of inner side with broad brown stripe which apically broadens (Fig. 55); femur 2 with brown stripes on distal third of inner and outer sides, femur 3 with brown stripes on distal quarter of inner and outer sides (Fig. 59); femur 1 (Figs 55, 58) incrassate, l/w ratio: 3.30 ± 0.02 (n = 16, Tables 3, 6), femur 1 much less incrassate than in other Centrioncus (see Tables 6, 7); two rows of spinous setae (Fig. 58) on distal two-thirds of femur 1 with 6.8 ± 0.2 setae (n = 31, Tables 3, 6), inner row with 3.7 ± 0.1 setae, outer row with 3.1 ± 0.0 setae; two rows of tubercles (Fig. 58) on distal three-quarters of femur 1 with 32.7 ± 0.6 tubercles (n = 31, Tables 3, 6), inner row with 15.2 ± 0.3 tubercles, outer row with 17.5 ± 0.4 tubercles; femur 3 ventrodistally with 4.9 ± 0.2 tubercles (n = 32) in single row (Fig. 59); setal formula: 3.1, 3.7, 17.5, 15.2, 4.9 agrees with formula of type series given by De Meyer (2004): 3, 3–4, 18, 15, 4.

Preabdomen. Tergites blackish brown, thinly pruinose, posterior edges somewhat paler, more pruinose; tergite 2 with small pale spots in posterolateral corners (Figs 55, 60); tergite 3 with pale posterior band (Fig. 60); sternites pale brown; lateral edges of membranous ventral areas with dark lateral spots; sternite 1 rectangular but somewhat constricted mesally (Fig. 72); sternite 2 slightly tapering posteriorly, no intersternite present, only mesal anterior edge of sternite 2 slightly more sclerotised (Fig. 72); sternite 3 rectangular, sternite 4 trapezoidal, broadening posteriorly (Fig. 72); sternite 5 rectangular; sternite 6 short and broad, almost as broad as segment (Fig. 68); sternites 1 and 2 glossy, other sternites pruinose (Fig. 72); first spiracle in membrane.

Female postabdomen. Seventh spiracle at edge of tergite (Fig. 62); anterior sclerite of sternite 7 with w/l ratio: 2.6 (3.1 in De Meyer 2004; fig. 6; see also Table 8), glossy on basal third but pruinose posteriorly (Figs 61, 62); posterior sclerite weakly U-shaped, with posterolateral extensions (Figs 61, 62), almost extending to posterior corners of tergite 7, lateral sections with characteristic outward curve, uniformly pruinose; tergite 8 consisting of two oblong plates, narrowly separated mesally, large central sections more sclerotised (Fig. 65); tergite 10 (Fig. 65) inverted mitre-shaped, extending posteriorly between cerci, clothed in microtrichia and with two pairs of setulae; cercus rather broad, l/w ratio: 2.3 (Fig. 65, Table 8); subanal plate (Figs 63) short, broad, almost triangular with rounded apex, ventrally clothed in microtrichia, with ~ 26 setulae on apical half, shape of subanal plate unusual in the genus (compare Fig. 63 vs. Figs 46, 84, 105, and Feijen (1983: figs 47–65); spermathecae well-sclerotised, smooth, rounded with shallow apical dimple (Fig. 64), junction of ducts of paired spermathecae V-shaped.

Figures 61–67. 

Centrioncus bytebieri, ♀ 61 Ngangao Forest 62–67 Vuria Forest 61, 62 sternite 7, ventral view 63 subanal plate ventral view 64 spermathecae 65 sternites 8, 10, cerci, ventral view 66 egg 67 egg, detail. Scale bars: 0.2 mm (61, 62, 66); 0.1 mm (63–65, 67).

Male postabdomen. Epandrium, cerci and surstyli of additional specimens conform to drawings and description by De Meyer (2004) (Figs 68–70); microtrichia on outer side of surstylus shown in Fig. 70; common base of outer and median arm of surstylus long and slender; outer arm with 6–9 tubercles; median arm with six dark, spinous setae apically; inner arm of surstylus two-thirds length of median arm; subepandrial clasper (Figs 69, 70) trapezoidal, basally narrower, mesal apical corner rounded, lateral apical corner distinctly pointed, glabrous, with ~ 11 setulae on inner side; cercus (Fig. 71, Table 8) with broad lateral extension distally, with “foot” slightly concave distally, length/greatest width ratio: 1.7 (Table 8); ejaculatory apodeme + sac (Fig. 73, Table 9) very large, 11.6% of body length, apodeme club-shaped, basally slender.

Figures 68–73. 

Centrioncus bytebieri, ♂, Vuria Forest 68 synsternite 7+8, epandrium, surstyli, lateral view 69 subepandrial clasper and surstylus, inner view 70 subepandrial clasper and surstylus, outer view 71 cercus, posterior view 72 sternites 1–5, ventral view 73 ejaculatory apodeme + sac. Scale bars: 0.2 mm (68, 72); 0.1 mm (69–71, 73).

Egg. Female from Ngangao carried nine developed and developing eggs in abdomen; eggs (Figs 66, 67) ≤ 1.04 mm in length; slightly elevated longitudinal ridges spanning from anterior pole to posterior pole with fine, nearly hexagonal microstructure between ridges (Fig. 67).

The localities of the type series and the specimens now studied are indicated on the map for Eastern Africa (Fig. 29). The distribution appears to be limited to the Taita Hills, a Precambrian mountain range located in the Taita-Taveta County in south-eastern Kenya. These hills consist of three massifs: Dabida (Dawida), Sagalla and Kasigau. Centrioncus bytebieri is only known from the Dabida Massif. No Centrioncus are known from Sagalla, while C. copelandi sp. nov. occurs in Kasigau. The type series was collected in the forest remnants of the Dabida complex in the Ngangao, Chawia and Yale Forests, as well as in the Mbololo Forest. The new specimens also came from Ngangao, Chawia and Mbololo Forests, while as new locations the Fururu and Vuria Forests can now be added. De Meyer (2004) found that his collecting sites were situated from 1400–1800 m, while the specimens now studied were collected from 1680–2162 m. De Meyer added that the species is common and “found on leaves of lower vegetation (shrubs, plants), usually in shaded places in the forests.” The gravid female was collected in the last week of January/first week of February, just before the start of the long rains in Kenya. The male collected in the last week of July/first week of August proved to be teneral, so emerging after the end of the long rains.

The additional specimens were largely from the type locality. Male and female genitalia, but also external characters like colour pattern and large size, conform to the description by De Meyer (2004). However, some differences and additions should be indicated. For the pleura, the brown anepimeron and greater ampulla also form part of the large central brown area. The wing has a central wing spot. De Meyer’s description of the posterior sclerite of female sternite 7 was fine but the drawing (fig. 6) shows a rather small sclerite. De Meyer gave a very brief description of the subanal plate. As this plate is very characteristic, it needed redescription. De Meyer described the female cercus as “not so narrow” but gave as l/w ratio: 4.2, which differs from the ratio 2.3 found here. Additional or more detailed illustrations have now been provided for various characters.

Kenya, holotype, ♂, Coastal Prov., Kasigau Mtn, 3.82700°S, 38.64875°E, 1065 m, 28.xii.2011–11.i.2012, R. Copeland (NMKE). Paratype: 1 ♀, Coastal Prov., Kasigau Mtn, 3.82667°S, 38.64982°E, 1117 m, 30.vi–13.vii.2011, R. Copeland (NMKE).

Centrioncus copelandi sp. nov. can be recognised by a mesally slightly depressed, pruinose frons with glossy spots; glossy collar; pruinose blackish brown scutum; dark brown scutellum with brown edges and spines; pleura blackish brown (Figs 74, 76); scutellar spine/scutellum ratio: 0.87–1.00; apical seta/scutellar spine ratio: 0.86–0.92; brown, strongly incrassate fore femur (l/w ratio: ~ 2.65) with ~ 31.7 tubercles, dark brown stripe dorsally on apical third of inner side; very large, distinct central wing spot in distal third of cell br, basal two-fifths of cell r4+5 and distal two-thirds of cell bm+dm (Fig. 4); tergites blackish brown; female 7^th spiracle in tergite; sternite 4 rectangular; sternite 5 trapezoidal, invaginated anteriorly; sternites 4 and 5 with pair of strongly sclerotised spots; sternite 6 trapezoidal, 1.5× as broad as sternites 1–5; anterior sclerite of female sternite 7 with w/l ratio: ~ 3.1 (Fig. 81); posterior sclerite of female sternite 7 truncated U-shaped, straight anterior and lateral edges with angular anterolateral corners; female cercus elongate, l/w ratio: ~ 4.4; subanal plate pentagonal, apically tapering into short extension; spermathecae rounded, basally flat (Fig. 85), with small apical dimple; spermathecal ducts with constriction near spermathecae; outer and median arms of surstylus well separated, with short broad common base; outer arm constricted at base, apically broadening to 3× width of base, sides concave, with 16 apical tubercles (Fig. 88); median arm a slender rod, apically some long setulae but no spinous setae, slightly shorter than outer arm; inner arm twice as broad as median arm and slightly longer, apically with shape of cap opener; subepandrial clasper elongate, basal third constricted, apical corners angular, apically strongly convex; cercus (Fig. 89) with broad lateral extension on distal third, apically convex.

Figures 74–79. 

Centrioncus copelandi sp. nov., Kasigau Mtn 74 ♂, holotype, lateral view (abdomen removed) 75–79 ♀, paratype 75 head, frontal view 76 head posterolateral view, thorax, lateral view 77 abdomen, dorsal view 78 fore femur, ventral view 79 hind femur, ventral view. Scale bars: 0.5 mm.

Measurements. Body length ♀ 5.1 mm, ♂ 5.0 mm, width of head ♀ 1.08 mm, ♂ 1.13 mm, wing length ♀ 4.3 mm, ♂ 4.3 mm, length of scutellar spine ♀ 0.34 mm, ♂ 0.31 mm.

Head. Frons slightly depressed mesally, brown but mesally and anteriorly paler brown, black stripe posterior to FOS; frons pruinose, anterolaterally more densely pruinose, black stripe behind FOS glossy, small glossy spots lateral to ocellar tubercle (Fig. 75); occiput blackish brown, with lateroventral corners yellowish brown (Fig. 76), uniformly pruinose, more densely pruinose dorsomesally; face yellowish brown, pruinose, denser pruinosity along eye margins; antenna yellowish brown, funiculus with dark spot at base of arista; maxillary palpus dark; OVS 0.31 mm in ♀ and 0.29 in ♂, FOS 0.24 mm in ♀ and ♂.

Thorax. Collar glossy dark brown; scutum blackish brown, pruinose, posterior half of humeral callus glossy (Fig. 76); scutellum dark brown, pruinose, posterior and lateral edges and scutellar spines yellowish brown (Figs 74, 76); pleura dark brown, pleura mainly pruinose, glossy sections include anterior proepisternum, ventral edge of anepisternum, ventral half of katepisternum and ventral spot on anepimeron, densely pruinose spots on posterior section of anepimeron and dorsoposterior section of katepisternum (Figs 74, 76); posterior notopleural, supra-alar and infra-alar setae present, infra-alar seta twice as long as posterior notopleural and supra-alar setae, supra-alar seta on inconspicuous carina (Fig. 74); basiliform prosternum lanceolate and anteriorly sharply pointed and with line-like extension; scutal length/scutal width ratio: 1.1; scutellum projecting at angle of just > 20° from body axis; scutellar spines almost aligned with dorsal plane of scutellum, diverging at angle of ~ 50°; scutellar spine/scutellum ratio: 1.00 in ♀ and 0.87 in ♂; scutellar spine/length of body ratio: 0.067 in ♀ and 0.063 in ♂; apical seta/scutellar spine ratio: 0.86 in ♀ and 0.92 in ♂; scutellar length/scutellar width (at base) ratio: ~ 0.70.

Wing. Almost transparent with very large, distinct, brownish central spot in distal third of cell br, basal two-fifths of cell r4+5, distal two-thirds of cell bm+dm and slightly extending into cells r2+3, m1 and m4 (Fig. 4); glabrous basal areas only include cells bc and c and small basal and subbasal spots in cell br; crossvein h distinct; cell sc closed; vein CuA+CuP from vein CuP onward extending under angle of 25° to wing margin in almost straight line (Fig. 4); cell cua triangular; vein M4 continuing distal of crossvein dm-m in almost straight line to wing margin; alula distinct; crossvein bm-m very vaguely indicated.

Legs. Coxa 1 and trochanter 1 whitish (Fig. 76), thinly pruinose; femur 1 glossy, yellowish brown with dark brown stripe on apical third of dorsal part of inner side (Figs 74, 78); tibia 1 dark brown, pruinose; metatarsus 1 yellowish brown, other tarsal segments whitish; mid and hind legs pale yellowish brown; apex of femur 2 brown; femur 3 dark brown on apical seventh (Fig. 74); tibia 3 with brown spots basally and apically (Fig. 74); femur 1 strongly incrassate in ♀ and ♂ (Figs 74, 78), l/w ratio: 2.62 in ♀ (n = 1) and 2.67 in ♂ (n = 1), inner row of spinous setae (Fig. 78) with 4–5 setae (n = 3), outer row with 4 setae (n = 3), inner row of tubercles with 15.3 tubercles (range 15–16, n = 3), outer row with 16.3 tubercles (range 15–17, n = 3); femur 3 (Fig. 79) with 5.0 tubercles (range 4–6, n = 3); setal formula 4.0, 4.7, 16.3, 15.3, 5.0; femora 2 and 3 without apical spurs.

Preabdomen. Tergites blackish brown (Fig. 77), very thinly pruinose, posterior edges of tergites 2 and 3 with more densely pruinose band; sternites dark brown; lateral edges of membranous ventral areas with dark brown spots; sternite 1 rectangular, constricted mesally (Fig. 80); intersternite 1–2 very dark, laterally acuminate, with thin lateral connections to main sternite 2; sternite 2 rectangular, posterior of intersternite with small membranous area; sternite 3 rectangular with two narrow, elongate, more sclerotised areas (Fig. 80); sternite 4 rectangular with convex lateral sides and two distinct, heavily sclerotised spots anteriorly; sternite 5 trapezoidal, anteriorly strongly constricted mesally, with two distinct, heavily sclerotised spots anteriorly (Fig. 80); sternite 6 trapezoidal, ~ 1.5× as broad as sternites 1–5; sternites 1–3 glossy, sternites 1 and 3 with a few microtrichia laterally; sternites 4–6 pruinose; 1^st spiracle in membrane.

Figures 80–83. 

Centrioncus copelandi sp. nov., ♀, paratype, Kasigau Mtn 80 sternites 1–6, ventral view 81, 82 sternite 7, ventral view 83 terga 8, 10 and cerci, dorsal view. Scale bars: 0.2 mm

Female postabdomen. Tergite 7 brown, with mesal gap posteriorly, posterior gap extending to lateral sides, lateral edges curved under ventrally; suture in basal ring of segment 7 faint; 7^th spiracle well into tergite (Fig. 82); anterior sclerite of sternite 7 rectangular, slightly tapering posteriorly (Figs 81, 82), w/l ratio: ~ 3.1 (Table 8), dark brown, glossy on basal third, pruinose posteriorly (Figs 81, 82), with ~ 30 setulae; posterior sclerite of sternite 7 truncated U-shaped, consisting of broad anterior section and two broad lateral extensions (Figs 81, 82), anterior edge straight and parallel to posterior edge of anterior sternite, lateral edges of extensions straight and diverging posteriorly, anterolateral corners angular, posterolateral apices rounded, clothed in microtrichia and with four setulae at posterior apices; tergite 8 consisting of two oblong plates, well separated mesally (Fig. 83); sternite 8 consisting of two oblong plates; tergite 10 (Fig. 83) onion-shaped, extending posteriorly between cerci, clothed in microtrichia, with one pair of strong setulae; cercus elongate, somewhat tapering posteriorly (Fig. 83, Table 8), l/w ratio: ~ 4.4; subanal plate (Figs 83, 84) somewhat pentagonal, laterally rounded and apically tapering into short extension, clothed in microtrichia except anterior edge, with ~ 26 setulae; spermathecae heavily sclerotised, smooth, rounded, basally flattened (Fig. 85), with small apical dimple; junction of ducts of paired spermathecae V-shaped, spermathecal duct with distinct constrictions near junction with spermathecae (Fig. 85).

Figures 84–87. 

Centrioncus copelandi sp. nov., ♀, paratype, Kasigau Mtn 84 subanal plate, ventral view 85 spermathecae 86 egg 87 egg, detail of external microstructure. Scale bars: 0.1 mm (84, 85, 87); 0.2 mm (86).

Male postabdomen. Tergite 6, sternite 8 and epandrium uniformly blackish brown; epandrium broad and rounded (too damaged to measure w/l ratio), clothed in microtrichia; outer and median arms of surstylus well separated, with short broad common base (Fig. 88); outer arm deeply constricted at base with concave lateral sides, broadening apically to ~ 3× basal width, apically with row of 16 tubercles, basally with nine setulae (2 very long) on inner side and a few small setulae along apical edge, on outer side with a few small setulae and central patch of microtrichia; median arm (Fig. 88) slender, parallel-sided, rod-shaped, almost as long as outer arm, apically with four small setulae and two long setulae, no spinous setae present; inner arm twice as broad as median arm and slightly longer, apical quarter abruptly narrowed, cap opener-shaped, apically with seven setulae; subepandrial clasper (Fig. 90) somewhat elongate, basal third constricted, apical corners angular, apically strongly convex, glabrous, with four long setulae on inner side; cercus (Fig. 89, Table 8) slender, with broad lateral extension on distal third, apically convex, clothed in microtrichia and short setulae, 7 longer setulae along apical edge, length/greatest width ratio: 1.5 (Table 8); ejaculatory apodeme + sac (Fig. 91, Table 9) very large, 10.1% of body length, ejaculatory apodeme slender, apically broadening.

Figures 88–91. 

Centrioncus copelandi sp. nov., ♂, holotype, Kasigau Mtn 88 surstylus, inner view 89 cercus, posterior view 90 subepandrial clasper, posterior view 91 ejaculatory apodeme + sac. Scale bars: 0.1 mm.

Egg. Female with two damaged full-grown eggs and some pieces of undeveloped eggs in abdomen. Eggs (Fig. 86) measured 1.01 mm in length with elevated longitudinal ridges spanning from anterior pole to posterior pole with fine, roughly hexagonal microstructures between ridges (Fig. 87).

The localities of the type series are indicated on the map for Eastern Africa (Fig. 29). The collecting sites varied from 1056 to 1117 m in altitude. The habitat of the Kasigau site at 1117 m is shown in Fig. 92. The distribution appears to be limited to the Kasigau Massif of the Taita Hills (see also under C. bytebieri). Centrioncus bytebieri is only known from the Dabida Massif of the Taita hills. The gravid female was collected in early July, in the middle of the dry season which is unusual for Centrioncus flies.

Figure 92. 

Centrioncus copelandi sp. nov., Kenya, Kasigau Mtn, collection site at 1117 m. Photograph by Robert Copeland.

The specific epithet of C. copelandi sp. nov. refers to the name of its collector Dr Robert S. Copeland (ICIPE), who contributed a significant number of Centrioncus specimens to this study.

From the shape of the outer arm of the surstylus (apically much wider than at base, with large number of 16 or 17 tubercles), absence of spinous setae on the median arm of the surstylus, the very large central wing spot and anteriorly strongly constricted sternite 5, it can be postulated that the closest known relative of C. copelandi sp. nov. is C. prodiopsis. From a geographical point of view that also makes some sense (Fig. 29), although C. bytebieri occurs closer to C. copelandi sp. nov.

Angola, holotype, ♀, Salazar I.I.A.A. N’dalatando (Salazar) [most probably Instituto de Investigação Agronomica de Angola at Quilombo, 5 km to north of N’dalatando, 8°53'1"S, 14°44'59"E, 600– > 1000 m], 9–15.iii.1972, Southern African Exp. B.M. 1972, no collector given [probably leg. P.M. Hammond] (NHMUK).

Centrioncus crassifemur sp. nov. can be recognised by the mesally slightly depressed, pruinose frons; mainly pruinose collar; pruinose blackish brown scutum with brownish humeral calli; dark brown, pruinose scutellum with pale scutellar spines; pleura blackish brown with anterodorsal corner of anepisternum brown (Fig. 93); scutellar spine/scutellum ratio: 0.81; apical seta/scutellar spine ratio: 0.81; fore femur (Figs 93, 98) strongly incrassate (l/w ratio: 2.36) with ~ 41.5 tubercles, pale brown, on distal third dark brown on both sides; distinct central brownish wing spot around crossvein r-m in distal tip of cell br and basal fifth of cell r4+5, somewhat extending into cell bm+dm (Fig. 5); tergites dark brown, posterolateral corners of tergites 2–4 paler brown; female 7^th spiracle just in tergite; sternite 4 rectangular; sternite 5 square; sternite 6 trapezoidal, 1.5× as wide as sternites 1–5; anterior sclerite of female sternite 7 broad, very short (w/l ratio: ~ 8.6); posterior sclerite of female sternite 7 large, membranous, trapezoidal plate, two tiny more sclerotised sections in anterolateral corners (Figs 102, 104); female cercus elongate, l/w ratio: 4.3; subanal plate (Fig. 105) laterally rounded, pentagonal, apically pointed; spermathecae round in cross section, flattened with large apical dimple and central pinnacle (Figs 106, 107).

Figures 93–96. 

Centrioncus crassifemur sp. nov., ♀, holotype, N’dalatando 93 habitus, lateral view 94 basiliform prosternum, ventral view 95 head, frontal view 96 head, thorax, dorsal view. Scale bars: 0.5 mm (93, 95, 96); 0.2 mm (94).

Measurements. Body length ♀ 5.1 mm, width of head ♀ 1.23 mm, wing length ♀ 4.5 mm, length of scutellar spine ♀ 0.31 mm.

Head. Frons slightly depressed mesally, dark brown, with lateral margins pale brown, mainly pruinose except glossy areas lateral to ocellar tubercle (Figs 95, 96); occiput glossy brown with some pruinescence posteriorly to ocellar tubercle and densely pruinose margins near eyes; face yellowish brown, thinly pruinose, with denser pruinosity along eye margins (Fig. 95); antenna yellowish brown, dorsal section of funiculus and basal segments of arista darker (Figs 95, 96); maxillary palpus dark; outer vertical seta 0.30 mm, fronto-orbital seta 0.18 mm.

Thorax. Collar dark brown, mainly pruinose, mesally and anteriorly glossy (Fig. 96); scutum blackish brown and pruinose, humeral callus brown and more glossy (Figs 93, 96); scutellum dark brown, pruinose; scutellar spines pale, but narrowly brownish basally (Figs 93, 96); pleura dark brown with only anterodorsal corner of anepisternum paler brown; pleura mainly thinly pruinose, densely pruinose areas around and below anterior spiracle, anterior and posterior sections of anepisternum, and dorsal anterior and posterior sections of katepisternum, glossy sections include ventral edge of anepisternum and ventral half of katepisternum (Fig. 93); posterior notopleural seta, supra-alar and infra-alar setae present, supra-alar seta ca. two-thirds length of other two setae; basiliform prosternum lanceolate and sharply pointed anteriorly (Fig. 94); scutal length/scutal width ratio: 1.22 (Fig. 96); scutellum projecting at angle of ~ 20° from body axis; scutellar spines almost aligned with dorsal plane of scutellum (Fig. 93), diverging at angle of just > 30°; scutellar spine/scutellum ratio: 0.81; scutellar spine/length of body ratio: 0.06; apical seta/scutellar spine ratio: 0.81; scutellar length/scutellar width (at base) ratio: 0.74.

Wing. Almost transparent but slightly tinged; distinct central brownish spot around crossvein r-m in distal tip of cell br and basal fifth of cell r4+5, somewhat extending into cell bm+dm (Fig. 5); some infuscation around vein M4 proximal to crossvein dm-m; glabrous basal areas only include cells bc and c and basal third of cell br; crossvein h distinct; cell sc closed; vein CuA+CuP from vein CuP onward extending under angle of 25° to wing margin in almost straight line; vein M4 continuing distal of crossvein dm-m in almost straight line towards wing margin; cell cua subtriangular; alula distinct; crossvein bm-m vaguely indicated.

Legs. Fore coxa and trochanter yellowish white, thinly pruinose; fore femur glossy, pale brown with darker brown apex (Figs 93, 97–99); fore tibia glossy brown with paler, more pruinose base; fore metatarsus yellowish brown, other tarsal segments whitish (Fig. 93); mid and hind legs pale yellowish brown, apical quarter of hind femur brown (Fig. 100); fore femur strongly incrassate in ♀ (Figs 97–99), l/w ratio: 2.36 (n = 1), fore femur subbasally connected to trochanter (Fig. 98) on inner side [assumed adaptation to very incrassate femora], inner row of spinous setae (Fig. 98) with five setae, outer row with four setae, inner row of tubercles with 20–21 tubercles, outer row with 21 tubercles; hind femora with six and nine (Fig. 100) tubercles; setal formula 4.0, 5.0, 21.0, 20.5, 7.5; no apical spurs on mid and hind femora.

Figures 97–100. 

Centrioncus crassifemur sp. nov., ♀, holotype, N’dalatando 97 fore femur, outer view 98 fore femora, ventral view 99 fore femur, inner view 100 hind femur, inner view. Scale bars: 0.2 mm.

Preabdomen. Dark brown, thinly pruinose, posterolateral corners of tergites 2–4 paler brown, posterior half of tergite 7 pale brown (Fig. 93); sternites 1–6 brown, sternites 1 and 2 glossy, sternites 3–6 pruinose; sternite 1 slightly trapezoidal (Fig. 101); sternite 2 anteriorly with very slender, more sclerotised section mesally with two minute setulae laterally; sternites 2–4 all rectangular, slender, more or less equal in width; sternite 5 square; sternite 6 (Fig. 102) trapezoidal, ~ 1.5× as wide as sternites 1–5; 1^st spiracle in membrane.

Figures 101–105. 

Centrioncus crassifemur sp. nov., ♀, holotype, N’dalatando 101 sternites 1–5, ventral view 102 sternites 6–8, subanal plate, cerci, ventral view 103 tergites 8, 10, cerci, dorsal view 104 sternite 7, ventral view 105 subanal plate, ventral view. Scale bars: 0.5 mm (101, 102); 0.1 mm (103–105).

Female postabdomen. Tergite 7 (Fig. 104) with large mesal gap posteriorly, lateral edges only marginally curved under ventrally; suture in basal ring of segment 7 hardly visible; 7^th spiracle at edge of tergite (Fig. 104); anterior sclerite of sternite 7 rectangular, broad and very short, w/l ratio: ~ 8.6, covered with microtrichia and some setulae on posterior half (Fig. 104, Table 8); posterior sclerite of sternite 7 trapezoidal plate, weakly sclerotised with two very small more sclerotised sections in anterolateral corners (Fig. 104), covered with microtrichia and with ~ 10 setulae posteriorly; tergite 8 consisting of two oblong plates, narrowly separated mesally, central sections more sclerotised (Fig. 103); sternite 8 consisting of two oblong plates, expanding posteriorly, and posteriorly linked mesally (Fig. 102); tergite 10 (Fig. 103) somewhat onion-shaped, extending posteriorly between cerci, laterally bare, otherwise clothed in microtrichia and with two pairs of setulae; cercus elongate, l/w ratio: 4.3 (Table 8); subanal plate (Figs 102, 105) laterally rounded, apically pointed, subpentagonal, ventrally covered with microtrichia and > 20 setulae on apical half; spermathecae heavily sclerotised, smooth, round in cross section, flattened with large apical dimple and peculiar central pinnacle (Figs 106, 107); junction of ducts of paired spermathecae V-shaped (Figs 106, 107).

Figures 106–109. 

Centrioncus crassifemur sp. nov., ♀, holotype, N’dalatando 106, 107 spermathecae 108 egg (transmitted light) 109 egg, detail (reflected light). Scale bars: 0.1 mm.

Egg. Holotype with six almost fully developed eggs in abdomen. Eggs (Figs 108, 109) measured 0.9 mm in length, with longitudinal ridges spanning from anterior pole to posterior pole with fine, nearly hexagonal, microstructures on and in between ridges. With different illumination settings, either ridges become more distinct (Fig. 109) or hexagonal microstructures (Fig. 108).

The single known specimen is from north-western Angola. The holotype was most likely collected in rain forest around the experimental station of the Instituto de Investigação Agronomica de Angola at Quilombo. The altitude of the collecting locality must then have been between 600 and slightly > 1000 m. The gravid holotype was collected in early March, which falls in the second half of the rainy season in Angola.

The specific epithet of C. crassifemur sp. nov. refers to the remarkably incrassate fore femora.

The more sclerotised anterior margin of sternite 2 forms an integral part of sternite 2 (Fig. 101) and is not, like in other Centrioncus, with thin lateral connections tied to the main region of sternite 2. Given the shape of the posterior sclerites of female sternite 7, the closest known relative of C. crassifemur sp. nov. could be C. aberrans. However, it is possible that the shape of sternite 7 simply represents a symplesiomorphic condition. Centrioncus aberrans and C. bururiensis sp. nov. are geographically speaking its closest known relatives.

Ivory Coast, holotype ♀, Amanikro, 50 km nw of Abengourou [7°1'0"N, 3°52'0"W, 52 km NW of Abengourou, 194 m], ix. 1961, J. Decelle (MRAC) (not examined, but notes and pencil drawings for Feijen (1983) were used).

(after Feijen 1983). Centrioncus decellei can be recognised by the flat, uniformly pruinose frons; pruinose blackish brown scutum, brownish humeral calli, chestnut-brown lateral edges; scutellum blackish brown with brown edges and lateral sides, scutellar spines yellowish; blackish brown pleura, brown anterior part of anepisternum and posterior part of anepimeron, katepisternum with brown spot anteriorly; scutellum projecting at angle of 45° from body axis; pale brown fore femur on distal half of inner side with dark brown, stripe-like spot, with ~ 38 tubercles; small, elongate, very vague, brownish central spot around crossvein r-m (Fig. 110), in tip of cell br, mainly in posterior part of basal quarter of cell r4+5, slightly extending into cell bm+dm; vein M4 distally of crossvein dm-m curving downward towards wing margin; tergites blackish brown, apical edges paler; female 7^th spiracle in tergite (Fig. 111); female tergite 7 with small mesal gap at posterior edge; female tergite 10 with 3 pairs of setulae; trapezoidal anterior sclerite of female sternite 7 narrow (w/l ratio: ~ 2.7); posterior sclerite of female sternite 7 rounded U-shaped, relatively short lateral arms with tri-lobed posterior apices (Fig. 111); female cercus elongate, l/w ratio: 4.1; subanal plate triangular, with convex lateral sides; spermathecae wrinkled, with a dimple and some tiny tubercles.

Figures 110, 111. 

Centrioncus decellei, ♀, holotype, Amanikro, Ivory Coast 110 wing, dorsal view 111 sternite 7, ventral view. Scale bars: 0.5 mm (110); 0.1 mm (111). Both drawings were processed, based on original pencil drawings from Feijen (1983: figs 12, 26).

Wing. Small, elongate, very vague, brownish central spot around crossvein r-m (Fig. 110), in tip of cell br, mainly in posterior part of basal quarter of cell r4+5 to three-quarters distance to crossvein dm-m, slightly extending into cell bm+dm; vein CuA+CuP from vein CuP onward extending under angle of 25° to wing margin in straight line; vein M4, especially distal of crossvein dm-m, curving downward to wing margin (Fig. 110).

Female postabdomen. Anterior sclerite of sternite 7 trapezoidal with w/l ratio: ~ 2.7 (Fig. 111, Table 8); posterior sclerite of sternite 7 rounded U-shaped, with relatively short lateral arms, with 3–4-lobed posterior apices (Fig. 111); female cercus elongate with l/w ratio: 4.1 (Table 8); subanal plate triangular with convex lateral sides.

There are several Amanikro locations in Ivory Coast, three of which are north-west of Abengourou. However, given the label distance of 50 km from Abengourou, the correct collecting location must be Amanikro at 7°1'0"N, 3°52'0"W, 52 km NW of Abengourou, 194 m. The holotype was collected in lowland forest. This species is the only Centrioncus known to occur at a low altitude, while the single specimen is also the only Centrioncus known from West Africa.

Kenya, holotype ♂, Naivasha [0°41'40"S, 36°22'47"E], vii.1937, H.J.A. Turner (NHMUK). Paratypes: 1 ♀, 1 ♂, same data as holotype; 1 ♀, 1 ♂, Thomson’s Falls [now Nyahururu Falls, 0°2'38.98"N, 36°22'13.04"E], x.1934, F.W. Edwards (NHMUK); 1 ♂, Chania Falls, Aberdare range [0°27'16.70"S, 36°43'1.28"E], x.1934, F.W. Edwards (NHMUK); 1 ♀, Ngong [1°21'22"S, 36°40'8"E], ix.1940, G. van Someren (NHMUK).

Kenya: 27 ♀, 25 ♂, Naro Moru River, [0°9'22.93"S, 37°0'50.45"E, 1950 m], 20.vii.1987, H.R. Feijen (RMNH); 6 ♀, 6 ♂, Limuru nr Mrs Mitchels tea plantation, Rain forest, Kiambethu Tea Plantation, [1°7'3.18"S, 36°40'58.11"E, 2167 m], 3.ix.1986, Cobi Feijen (RMNH); 2 ♀, 2 ♂, nr Namanga Tanzania [but in Kenya], Ol Doinyo Orok forest, [~ 2°31'S, 36°47'E, ~ 1800 m], 0.iii.1986, J. Muhangani (RMNH); 1 ♀, 1 ♂, Thomson’s falls, Nyahururu, [0°2'38.98"N, 36°22'13.04"E, 2329 m], 20.iii.1988, H.R. Feijen (RMNH); 3 ♀, 3 ♂, Nyahuru(ru), Upper Imenti Forest, Meru Distr. E. Kenya, [0°3'0"N, 37°31'59"E], vii.1973, E. Balyetagara (CNC); 2 ♀, 3 ♂, Laikipia Co., Thomson’s Falls env. (= Ngare Naro forest), 0.047°N, 36.377°E, 25.xi.2012, D. Gavryushin (ZMUM); 3 ♀, 1 ♂, Laikipia Co., Thomson’s Falls env., 0.047°N, 36.377°E, 21–23.xii.2013, N. Vikhrev (ZMUM); many (photograph), Ngare Naro forest (near Thomson’s Falls), 27.xi.2012, D. Gavryushin; 2 ♀, 2 ♂, Central Province, Katura Forest, Nairobi, shaded mixed upland indigenous forest, 1°14.504'S, 36°49.452'E, 1720 m, 23.iv.2011, A.H. & M.K. Kirk-Spriggs (BMSA); 3 ♀, 1 ♂, Eastern Prov., Nyambene Hills, Itieni forest, at bottom, malaise trap, edge indigenous forest, 0.24433°N, 37.87016°E, 2142 m, 1 ♀ 1 ♂ 2–16.x.2011, 1 ♀ 18.ix–2.x.2011, 1 ♀ 15–29.xi.2011, R. Copeland (ICIPE); 1 ♀, Central Prov., Ngong road forest, Nairobi, fogging, 1°18'57"S, 36°44'27"E, ~ 1830 m, 12–14.ii.1999, T. Wagner (ICIPE); 2 ♀, 3 ♂, Eastern Prov., Njuki-Ini Forest, near forest station, sweep net, edge indigenous forest, 0.51660°S, 37.41843°E, 1455 m, 13.ii.2011, R. Copeland (ICIPE); 1 ♀, 2 ♂, Gatama(i)yu forest, near fishing camp, malaise trap, 0°58.68'S, 36°41.62'E, ~ 2246 m, 20–27.iii.1999, R. Copeland (ICIPE). In total 53 ♀and 49 ♂ were examined.

Centrioncus decoronotus can be recognised by the mesally depressed, pruinose frons with glossy spots; glossy collar; scutum with configuration of blackish brown and brown (Figs 112, 113, 117), basic colour chestnut brown (including humeral calli), blackish sutures around humeral calli, blackish mesal stripe on anterior half, square, mesal, blackish area posteriorly of intrascutal sutures; scutellum brown, dorsally darker, scutellar spines brown; pleura blackish brown (Figs 113, 117) with chestnut brown anterodorsal anepisternum, greater ampulla and posterior anepimeron; scutellar spine/scutellum ratio: 0.90; apical seta/scutellar spine ratio: 0.91; yellowish brown, strongly incrassate fore femur (l/w ratio: 2.89) with ~ 34.5 tubercles; brown stripe dorsally on distal half of inner side (Figs 113, 114); large central wing spot (Fig. 6), mainly in basal section of cell r4+5 till just apically of crossvein dm-m, extending into cell br, cell r2+3 and cell bm+dm; tergites dark brown, thinly pruinose, posterolateral corners whitish pruinose; sternite 4 rectangular, laterally two more sclerotised sections, anteriorly 2 pairs of tiny heavily sclerotised spots (Fig. 118); sternite 5 broadening posteriorly, laterally more sclerotised, 1 pair of strongly sclerotised spots anteriorly; sternite 6 trapezoidal, posteriorly 1.6× as wide as sternites 1–4, two more sclerotised plates anteriorly; female tergite 7 with serrated lateral edges; female 7^th spiracle in tergite; anterior sclerite of female sternite 7 short (Table 8), w/l ratio: ~ 3.9 (Fig. 119); posterior sclerite of female sternite 7 U-shaped, posterior apices sometimes slightly broadening (Fig. 119); female cercus rather elongate with l/w ratio: 3.6; subanal plate pentagonal, laterally convex, apex acuminate; spermathecae round, somewhat wrinkled, distinct dimple, some tiny tubercles (Fig. 120); common base of outer and median arm of surstylus long, slender; outer arm rounded, deeply constricted near median arm, largest width 1.8× width at base, 4–6 tubercles apically (Fig. 122); median arm slender, rod-shaped, much longer than outer arm, three or four spinous setae apically; inner arm apically acuminate, shorter and narrower than median arm, no apophysis; subepandrial clasper triangular, basal two-thirds narrow, medial apical corner angular, lateral corner extended (Figs 122, 124); cercus (Fig. 123) with broad lateral extension on distal third, apically slightly concave.

Figures 112–116. 

Centrioncus decoronotus 112, 113 ♀, Thomson’s Falls 114, 115 ♂, Itieni Forest 116 ♂, Katura Forest 112 thorax, dorsal view 113 head, thorax, lateral view 114 fore femur, inner view 115 hind femur, inner view 116 head, frontolateral view. Scale bars: 0.2 mm (112, 114–116); 0.5 mm (113).

Figure 117. 

Centrioncus decoronotus, ♂, Nyahururu, Ngare Naro Forest. Photograph by D. Gavryushin.

Figures 118–121. 

Centrioncus decoronotus, ♀, Ol Doinyo Orok 118 sternites 1–5, ventral view 119 sternite 7, ventral view 120 spermathecae 121 egg, detail of external structure (L = line, R = ridge). Scale bars: 0.2 mm (118, 119); 0.05 mm (120, 121).

The biometrical data are presented for the series now studied, and compared to the type series. Additional morphological data as well as a few rectifications are presented. Various aspects of the morphology are now illustrated by photographs, while line drawings are presented for flies from Ol Doinyo Orok, a location distant from the type location.

Measurements. For type series of 3 ♀ and 4 ♂, Feijen (1983) provided the following measurements: body length ♀ 5.3 mm and ♂ 5.2 mm, head width ♀ 1.23 mm and ♂ 1.17 mm, wing length ♀ 5.0 mm and ♂ 4.7 mm, scutellar spine length ♀ 0.36 mm and ♂ 0.31 mm. For the much larger series now available, 22 ♀ and 22 ♂ were measured in more detail. In Table 4, measurements and other quantitative characters are presented for this series. In this table, data are presented for females and males separately. The table shows that differences between females and males for quantitative characters are marginal. The body length and various other measurements are slightly larger in the females. In Tables 6, 7 the data for females and males are combined, so that large series can be compared with the other Centrioncus species for which large numbers were available. The original measurements of the type series fall well within the ranges provided here: body length 5.15 mm ± 0.04 (range 4.64–5.61, n = 44), head width 1.14 mm ± 0.01 (range 1.02–1.24, n = 44), wing length 4.51 mm ± 0.03 (range 4.09–5.00, n = 39), scutellar spine length 0.33 mm ± 0.00 (range 0.29–0.37, n = 44).

Colour. The specific epithet decoronotus refers to the colourful notum of the mesothorax with its pattern of brown and blackish brown. This pattern is shown well in the fly from the Thomson’s Falls (Fig. 112), but is much less pronounced to almost absent in flies from Katura Forest. This is not only due to preservation techniques, but is present in live specimens as can be observed in photographs of live flies from Ngare Naro forest (near Thomson’s Falls) where the pattern is also less pronounced (Fig. 117).

Head. Frons mesally depressed, pruinose with glossy spots lateral to ocellar tubercle (Fig. 116), face yellowish brown; occiput mainly blackish brown, ventral edge of occiput and postgena yellowish (Fig. 113), thinly pruinose, with median occipital sclerite densely pruinose; length of outer vertical seta 0.34 mm ± 0.00 (n = 35, Tables 4, 7); length of fronto-orbital seta 0.22 mm ± 0.00 (n = 35). In highly enlarged photographs, mid facial region densely microtrichose, with row of microtrichia near eye margin (McAlpine 1997: figs 21, 22) (see also Fig. 116).

Thorax. Collar glossy blackish brown (Figs 112, 117); scutum and pleura show typical configuration of blackish brown and brown (Figs 112, 113, 117); humeral callus brown (not blackish brown as described by Feijen (1983: fig. 7)); scutellar spine/scutellum ratio: 0.90 ± 0.01 (n = 44, Tables 4, 7); scutellar spine/body length ratio: 0.063 ± 0.001 (n = 44); apical seta/ scutellar spine ratio: 0.91 ± 0.01 (n = 21, range 0.83–1.03; Table 7); scutellar length/scutellar width (at base) ratio: 0.64; supra-alar carina with supra-alar seta illustrated by McAlpine (1997: fig. 35), seta difficult to see in Figs 112, 113.

Wing. Large, central wing spot, mainly in basal section of cell r4+5, extending into cell br, cell r2+3 and cell bm+dm (Fig. 6); distinct infuscation along central section of vein M4; some variability in intensity of central spot, specimens from Katura forest have, for instance a darker spot than specimens from Naro Moru; two vague apical wing spots mentioned by Feijen (1983) in cells r2+3 and r4+5 often not visible; vein M4 continuing distal of crossvein dm-m in straight line to wing margin; vein CuA+CuP from vein CuP onward extending under angle of 30° to wing margin in almost straight line; cell cua triangular.

Legs. Femur 1 with distinct brown stripe (Figs 113, 114, 117) dorsally on distal half of inner side, not vague as stated by Feijen (1983); femur 1 strongly incrassate, l/w ratio: 2.89 ± 0.01 (n = 43, Tables 4, 7); two rows of spinous setae (Fig. 114) on distal two-thirds of femur 1 with 8.4 ± 0.1 setae (n = 72, Tables 4, 7), inner row with 4.5 ± 0.1 setae, outer row with 3.9 ± 0.0 setae; two rows of tubercles (Fig. 114) on distal three-quarters of femur 1 with 34.5 ± 0.3 tubercles (n = 71, Tables 4, 7), inner row with 16.4 ± 0.1 tubercles and outer row with 18.1 ± 0.2 tubercles; femur 3 (Fig. 115) distally with 4.9 ± 0.1 tubercles (n = 83, Tables 4, 7) in single row, except for 1 ♀ and 1 ♂ with each one tubercle in second row; setal formula 3.9, 4.5, 18.1, 16.4, 4.9 agrees well with formula of type-series given by Feijen (1983): 4.0, 4.3, 17.8, 17.0, 4.9.

Preabdomen. Tergites blackish brown, thinly pruinose, with whitish pruinose posterolateral corners; female tergite 7 less dark and glossier; posterolateral corners of tergite 2 more densely pruinose; sternites pale brown; membranous ventral areas with large dark lateral spots (Fig. 117); sternite 1 rounded rectangular, anteriorly strongly constricted mesally (Fig. 118); intersternite 1–2 dark, laterally acuminate, with thin lateral connections to main sternite 2; sternites 2–4 rectangular (Fig. 118), slender, more or less of equal width; sternite 5 somewhat broadening posteriorly; sternite 6 trapezoidal, posteriorly ~ 1.6× as wide as sternites 1–4 (Fig. 118); sternite 4 laterally with two ill-defined more sclerotised sections and two pairs of small heavily sclerotised sections anteriorly (Fig. 118); sternite 5 laterally with more sclerotised sections, anteriorly with pair of strongly sclerotised plates; sternite 6 more vaguely sclerotised laterally and anteriorly with pair of strongly sclerotised plates; sternites 1 and 2 glossy, sternite 1 with some microtrichia laterally, sternite 2 with some microtrichia in posterolateral corners; sternites 3–6 pruinose.

Female postabdomen. Tergite 7 with slightly serrated lateral edges (Fig. 119); 7^th spiracle in tergite; anterior sclerite of sternite 7 relatively short with w/l ratio: 3.9 (Table 8); posterior sclerite U-shaped; anterior and posterior sclerites of sternite 7 of ♀ from Ol Doinyo Orok forest similar to paratype illustrated by Feijen (1983), but posterolateral sections of posterior sclerite somewhat expanded (Fig. 119); cercus rather elongate, l/w ratio: 3.6 (Table 8); spermathecae of Ol Doinyo Orok ♀ (Fig. 120) similar to type series.

Male postabdomen. Genitalia identical with illustrations by Feijen (1983) but can be annotated as follows: for ♂ from Ol Doinyo Orok forest, surstylus, subepandrial clasper, cercus and ejaculatory apodeme + sac illustrated (Figs 122–125), as location is furthest removed from localities of type series; median arm of surstylus curved, long (Fig. 122) (due to curve median arm appears slightly shorter in Feijen (1983: fig. 140); outer arm of surstylus with 4 tubercles (and 1 underdeveloped one) (average of 6.0 tubercles (n = 4) in Feijen (1983)); median arm and basal half of outer arm clothed in microtrichia on outer side; 3-dimensional character of subepandrial clasper with small differences (compare Figs 122, 124 vs. Feijen 1983: fig. 141), very constricted basal section of subepandrial clasper, mentioned by Feijen (1983), also found in Ol Doinyo Orok ♂; cercus (Fig. 123, Table 8) with broad lateral extension on distal third, apically slightly concave, length/greatest width ratio: 1.4; ejaculatory apodeme + sac/length of body ratio: 16.5% (paratype from Chania Falls with ratio 16.3%) (Figs 125, 153).

Figures 122–125. 

Centrioncus decoronotus, ♂, Ol Doinyo Orok 122 left subepandrial clasper and surstylus, inner view 123 cercus, posterior view 124 right subepandrial clasper, posterior view 125 ejaculatory apodeme + sac. Scale bars: 0.1 mm (122–124); 0.2 mm (125).

Egg. Female from Ol Doinyo Orok forest with two almost fully developed eggs in abdomen. Eggs measured respectively 0.99 mm and 1.00 mm in length with longitudinal ridges spanning from anterior pole to posterior pole; in addition, more simple “lines”. Ridges (indicated with R) with tiny elongate pits along their length, while lines (indicated with L) form more integral part of roughly hexagonal microstructures between ridges (Fig. 121).

The collecting localities are shown on the map for Eastern Africa (Fig. 29). Centrioncus decoronotus was now found at altitudes varying from 1455–2329 m. Feijen (1983) reported it as occurring between 1200–2350 m. The eastern branch of the Great Rift Valley appears to form a barrier between C. decoronotus and C. aberrans. The gravid female was collected in March at the beginning of the long rains.

Feijen (1983) described the lateral sides of female tergite 7 as “rather irregular”, but showed the same serrated edges in his fig. 28, as now found in the specimen from Ol Doinyo Orok (Fig. 119). Other species of Centrioncus or Teloglabrus with serrated sides of tergite 7 are not known. The paratype from Thomson’s Falls had with 16.3% the highest ejaculatory apodeme + sac/length of body ratio. The Ol Doinyo Orok ♂ had with 16.5% a similar giant ejaculatory apodeme + sac (Table 9).

Malawi, holotype ♂, Limbe [Blantyre], Mount Soche [15°50'21"S, 35°1'10"E], 1300–1400 m, 22.x.1972, H.R. & J.J. Feijen (RMNH). Paratypes: 3 ♀, 2 ♂, same data as holotype; 7 ♀, 4 ♂, Limbe, Mount Soche, 1300–1400 m, 27.ii.1972; 2 ♀, 3 ♂, Limbe, Mount Soche, 1300–1400 m, 19.iii.1972, H.R. Feijen; 1 ♀, Mount Chiradzulu [Chiradzulu district, near Limbe, 15°41'47.11"S, 35°10'34.20"E], 1300–1350 m, 7.v.1972, H.R. Feijen; 1 ♀, 9 ♂, Limbe, Mount Ndirande [15°45'28"S, 35°3'19"E], 1400 m, 16.xi.1974, H.R. & J.J. Feijen. Next to the holotype, 14 ♀ and 18 ♂ paratypes were traced in the RMNH collections. This is slightly different from the 15 ♀ and 15 ♂ paratypes mentioned by Feijen (1983).

Malawi: 3 ♀, Limbe, Mount Ndirande [15°45'28"S, 35°3'19"E], 1400 m, 23.iv.1972, H.R. & J.J. Feijen (RMNH); 4 ♀, 5 ♂, Limbe, Mount Soche, [15°50'21"S, 35°1'10"E], 1300–1400 m, 7.viii.1974, H.R. Feijen (RMNH); 1 ♂, Limbe, Mount Soche, 1300–1400 m, 1972–1975, H.R. Feijen (RMNH); 3 ♀, 5 ♂, Limbe, Mount Soche, 1300–1400 m, 19.iii.1972, H.R. Feijen; 3 ♀, 1 ♂, Limbe, Mount Soche, 1300–1400 m, 7.viii.1974, H.R. Feijen; 5 ♀, 5 ♂, Limbe, Mount Soche, 1300–1400 m, 7.i.1973, H.R. Feijen; 3 ♂, Limbe, Mount Ndirande, 1400 m, 10.vii.1975, H.R. & J.J. Feijen. Including the type series, a total of 32 ♀ and 39 ♂ were collected from 1972–1975. This additional material was not included in Feijen (1983) because the author was working in Mozambique and later Zanzibar and did not transport the whole series to those countries.

Centrioncus jacobae can be recognised by the mesally slightly depressed pruinose frons with glossy areas (Fig. 128); glossy collar; thinly pruinose scutum with typical configuration of blackish brown and chestnut-brown (Figs 126, 127), brown humeral calli and laterally large brown presutural and postsutural areas; scutellum brown, pale brown scutellar spines; pleura chestnut-brown, blackish area around anterior spiracle, blackish posterior third; scutellar spine/scutellum ratio: 0.78; apical seta/scutellar spine ratio: 1.11; pale, strongly incrassate fore femur (l/w ratio: 2.78) with ~ 33.3 tubercles, inner side with broad brown stripe on distal three-fifths (Fig. 130); large central wing spot (Fig. 7), covering more than basal third of cell r4+5, extending into cells br and bm+dm; tergites blackish brown, two striking, large rectangular pale spots in the posterolateral corners of tergite 2 (Fig. 135); sternite 4 rectangular, sternite 5 slightly broadening posteriorly, sternites 4 and 5 both with anterior pair of small heavily sclerotised spots (Fig. 132); sternite 6 trapezoidal, 1.5× as broad as sternites 1–5; female 7^th spiracle in tergite; anterior sclerite of female sternite 7 with w/l ratio: ~ 2.6; posterior sclerite of female sternite 7 smoothly curved, slender, semi-circular U-shaped (Fig. 133); female cercus rather elongate, l/w ratio: 3.2; subanal plate pentagonal, lateral and apical sides straight; spermathecae round, smooth, with dimple, some dispersed tiny tubercles; common base of outer and median arm of surstylus short, broad; outer arm rounded, elongate, basally strongly constricted, largest width 2.7× basal width, apically with ~ 7.6 tubercles (Fig. 138); median arm longer than outer arm, club-shaped, rather broad, apically with ~ 4.0 spinous setae; outer and median arm almost fully clothed in microtrichia on outer side; inner arm much shorter than median arm, apically rounded, halfway with a rounded apophysis (Fig. 138); subepandrial clasper triangular, basal third constricted, medial apical corner pointed, extended lateral corner rounded (Fig. 138); male cercus with a long lateral, parallel-sided extension on distal quarter.

Figures 126–131. 

Centrioncus jacobae, paratypes 126 Mt Ndirande 127–131 Mt Soche 126 ♂, habitus, lateral view 127 ♀, thorax, dorsal view 128 ♂, head, anterolateral view 129 ♀, basiliform prosternum, ventral view 130 ♀, fore femur, inner view 131 ♂, hind femur, inner view. Scale bars: 0.5 mm (126–128); 0.2 mm (129–131).

Figures 132–135. 

Centrioncus jacobae, ♀, paratype, Mt Soche 132 sternites 1–6, ventral view 133 sternite 7, ventral view 134 abdomen, ventral view 135 abdomen, dorsal view. Scale bars: 0.5 mm (132, 134, 135); 0.2 mm (133).

Biometrical data are given for the remeasured series. Additional morphological data and illustrations are also presented.

Measurements. Feijen (1983) measured 20 ♀and 26 ♂ and gave as results: body length ♀ 5.61 mm ± SE 0.07 (range 5.2–6.2) and ♂ 5.28 mm ± 0.04 (4.8–5.7), head width ♀ 1.19 mm ± 0.01 (1.08–1.28) and ♂ 1.15 mm ± 0.01 (1.00–1.21), wing length ♀5.02 mm ± 0.06 (4.6–5.5) and ♂ 4.70 mm ± 0.05 (4.4–5.1), scutellar spine length ♀ 0.289 mm ± 0.006 (0.25–0.33) and ♂ 0.273 mm ± 0.004 (0.23–0.31). Of the original type series, 10 ♀ and 10 ♂ were remeasured in detail. In Table 5, the new measurements and other quantitative characters are presented. In this table, data are presented for females and males separately. The table shows that differences between females and males for quantitative characters are small. Body length and various other measurements are slightly larger for the females.

The original measurements of the type series do not agree well with the measurements now recorded. The measurements now found for ♀ and ♂ combined are: body length 4.97 mm ± 0.06 (range 4.58–5.43, n = 20), head width 1.11 mm ± 0.01 (range 1.04–1.21, n = 20), wing length 4.28 mm ± 0.05 (range 3.78–4.64, n = 20), scutellar spine length 0.27 mm ± 0.00 (range 0.24–0.29, n = 20). This means that the present measurements for body length and wing length are ~ 10% less, while the measurements for head width and scutellar spine are ~ 5% less. The specimens of the type series were measured in Malawi while in fresh condition. This could only affect the body length measurements to a small extent but not the other measurements. The persistent differences are probably due to calibration errors. The new measurements now indicate C. jacobae as a species is clearly smaller than the other Centrioncus species for which large series could be measured. (Tables 6, 7).

In connection with ecological research in Malawi from 1971 to 1975, the weight of fresh flies was regularly determined. The weight of some C. jacobae flies was also determined. In August (in the non-reproductive phase) seven females weighed on average 4.2 mg, while six males weighed on average 3.4 mg.

Colour. In optimal conditions, this species presents a colourful pattern of blackish brown and chestnut brown on the thorax as described by Feijen (1983) and now illustrated (Figs 126, 127).

Head. Colour pattern of anterior and posterior sides of head shown in Figs 126, 128; length of outer vertical seta 0.33 mm ± 0.01 (n = 19), length of fronto-orbital seta 0.22 mm ± 0.01 (n = 18).

Thorax. Basiliform prosternum brown, slender, triangular and anteriorly acuminate (Fig. 129); scutellar spine/scutellum ratio: 0.78 ± 0.01 (n = 19, Tables 5, 7); scutellar spine/body length ratio: 0.054 ± 0.000 (n = 20); apical seta/scutellar spine ratio: 1.11 ± 0.02 (n = 17), Feijen (1983) described apical seta as being “as long as spine”, but seta is now shown to be slightly longer than spine; scutellar length/scutellar width (at base) ratio: 0.68.

Wing. Pale brownish with distinct, large central wing spot, covering more than basal third of cell r4+5 (just past crossvein dm-m), slightly extending into apex of cell br and extending into anterior section of cell bm+dm between crossveins (Fig. 7); distinct infuscation along crossvein dm-m and along vein M4 between cell cua and crossvein dm-m; vein CuA+CuP from vein CuP onward extending under angle of 30° to wing margin in almost straight line (very sightly curving downward); vein M4 continuing distal of crossvein dm-m in almost straight line to wing margin; cell cua triangular (Fig. 7).

Legs. Femur 1 (Figs 126, 130) strongly incrassate, l/w ratio: 2.78 ± 0.02 (n = 18, Tables 5, 7); two rows of spinous setae on distal two-thirds of femur 1 with 8.9 ± 0.1 setae (n = 39; Tables 5, 7), inner row with 4.9 ± 0.1 setae and outer row with 4.0 ± 0.1 setae; two rows of tubercles on distal three-quarters of femur 1 with 33.3 ± 0.3 tubercles (n = 36), inner row with 15.4 ± 0.2 tubercles and outer row with 17.8 ± 0.2 tubercles; femur 1 on inner side with broad brown stripe on distal three-fifths (Fig. 130); femur 3 (Fig. 131) distally with 6.0 ± 0.2 (n = 37), tubercles in single row but one specimen with one tubercle placed in second row. Results lead to setal formula: 4.0, 4.9, 17.8, 15.4, 6.0 which agrees well with formula of the type-series as given by Feijen (1983): 4.0, 4.7, 16.9, 15.4, 5.6.

Preabdomen. Tergites blackish brown (Figs 135, 136), almost glossy, but with some pruinosity, especially at posterior margins of tergites 2 and 3 (Fig. 136); tergite 2 with two striking, large, pale brown rectangular areas in posterolateral corners (Fig. 135); smaller pale brown spots in posterolateral corners of tergites 3, 4, and 5; sternites 1 and 2 and anterior half of sternite 3 dark brown, posterior half of sternite 3 and sternites 4–6 yellowish brown (Fig. 134); sternite 1 glossy but laterally with some pruinosity; sternite 2 glossy with pruinose posterior margin; sternites 3–6 pruinose (Figs 132, 134); membranous ventral areas with large dark lateral spots (Fig. 134); sternite 1 somewhat rectangular, with concave anterior and posterior sides (Fig. 132); intersternite 1–2 dark, laterally acuminate, with thin lateral connections to main sternite 2; sternite 3 rectangular; sternite 4 rectangular, sternite 5 slightly broadening posteriorly, both sternites with pair of tiny heavily sclerotised spots, and with slightly more sclerotised areas posterior to spots (Fig. 132); sternite 6 ~ 1.5× as broad as sternites 1–5, with convex lateral sides and somewhat broadening posteriorly.

Female postabdomen. Tergite 7 brown anteriorly and yellowish brown posteriorly (Fig. 135); anterior sclerite of sternite 7 rectangular, w/l ratio: ~ 2.6 (Figs 133, 134, Table 8), dark brown and glossy on anterior half, more yellowish brown and pruinose on posterior half; posterior sclerite of sternite 7 slender, rounded, U-shaped (Fig. 133), clothed in microtrichia and with four setulae at posterior apices; cercus rather elongate, l/w ratio: 3.2 (Table 8); 7^th spiracle in tergite (Fig. 133).

Male postabdomen. Lateral side of male postabdomen shown in Fig. 136; epandrium, surstylus and subepandrial clasper presented in Figs 137, 138; common base of outer and median arm of surstylus short, broad; outer arm rounded, elongate, basally strongly constricted, largest width 2.7× basal width, apically with 7.6 (range 7–9) tubercles (Figs 137, 138); median arm long (longer than outer arm), club-shaped, rather broad, apically with 4.0 (range 3–5) stout spinous setae; outer and median arm almost fully clothed in microtrichia on outer side; inner arm much shorter than median arm, apically rounded, halfway with a rounded apophysis (Fig. 138); subepandrial clasper triangular, basal third constricted, medial-apical corner pointed, extended lateral corner rounded (Figs 137, 138); cercus with broad lateral extension on distal third, length/greatest width ratio: 1.4 (Table 8); ejaculatory apodeme + sac very large, 11–14% of body length (Table 9).

Figures 136–138. 

Centrioncus jacobae, ♂, Mt Soche 136 holotype, abdomen, hind femur, lateral view 137 epandrium, surstyli, posterior view 138 paratype, subepandrial clasper and surstylus, inner view. Scale bars: 0.5 mm (136); 0.1 mm (137, 138).

This species occurs at altitudes between 1300 and 1400 m in rain forests on the mountains around Blantyre and Limbe in Malawi. The rain forest at Mount Ndirande is gone, but patches on Mount Soche remain. The largest patches of rain forest remain on Mount Chiradzulu. However, this latter remark is quite relative when Loveridge’s (1954) observations about the Chiradzulu forest are considered: “Unfortunately the forest was but a pitiful remnant of its former self, few of its trees exceeding thirty feet in height and even these patches of secondary growth were separated by bracken which had swept up from below” and “This deforestation has resulted in the drying up of many of the streams during much of the year”. The strong discontinuity of the habitat of Afromontane Forest Flies will obviously be reinforced by the ongoing deforestation.

In the period 1971–1975, extensive collecting of Diopsidae was carried out in Malawi. Regular sampling took place on other mountains in Malawi, like the Nyika Plateau, Ntchisi Mountain, Dedza Mountain, Zomba Plateau and Mount Mulanje. However, Centrioncus were never encountered on these other mountains.

Feijen (1983) remarked that Centrioncus jacobae was every now and then collected together with other diopsids, especially Diopsis phlogodes Hendel. However, this was a misidentification of a species of the D. cruciata species-group. Diopsis phlogodes is a junior synonym of the rice stem-borer D. longicornis Macquart (see Feijen 1985).

Tanzania, lectotype ♂ (designated by Feijen 1983), Kibonoto [Kibongoto 3°11'S, 37°06'E], Kilimandjaro [Kilimanjaro], 7.x.1905–06, 2000–3500 m, Y. Sjöstedt (NHRS). Paralectotypes: 1 ♀, same locality, 5.i.1905–06, 2000 m, Y. Sjöstedt (NHRS); 1 ♀ (no abdomen), same locality, ix.1905–06, 1300–1900 m, Y. Sjöstedt (NHRS); 1 ♂ (no abdomen, but genitalia drawn by Hennig prior to1950, who marked the drawings with “holotype C. prodiopsis”), same locality, 5.i.1905–06, 2000 m, Y. Sjöstedt (ZMHB).

Kenya: 2 ♀, Rift Valley Prov., Olloitokitok [Oloitokitok], malaise trap, indigenous forest, 2.94456°S, 37.50714°E, 11–25.xi.2011, 1853 m, R. Copeland (ICIPE).

Centrioncus prodiopsis can be recognised by mesally slightly depressed pruinose frons with two glossy spots; glossy collar; pruinose, blackish brown scutum, brown humeral calli; blackish brown scutellum with brown lateral sides; blackish brown pleura, brown propleuron with paler ventral half; scutellar spine/scutellum ratio: ~ 0.98; apical seta/scutellar spine ratio: ~ 1.02; pale, strongly incrassate fore femur (l/w ratio: 2.92) with ~ 31.1 tubercles, on inner side with brown stripe on distal two-fifths (Fig. 143); very large central wing spot (Fig. 8), covering nearly basal half of cell r4+5, extending into distal half of cell br, extending into distal two-thirds of cell bm+dm and well into cells r2+3, m1 and m4; tergites 1–6 uniformly blackish brown; female 7^th spiracle in tergite; sternite 4 rounded, anteriorly significant, rounded invagination; sternite 5 rounded trapezoidal, anteriorly significant, rounded invagination; sternites 4 and 5 with anterior pair of small heavily sclerotised spots (Fig. 146); sternite 5 half-length of sternite 4; sternite 6 trapezoidal, 1.4× as broad as sternites 1–5; anterior sclerite of sternite 7 trapezoidal, w/l ratio: ~ 2.5, posterior sclerite of sternite 7 rounded, broad U-shaped (Figs 147, 148); female cercus rather elongate, l/w ratio: 4.0; subanal plate pentagonal, laterally convex and with acuminate apex; smooth spermathecae, very large apical dimple, cup-shaped, some dispersed tiny tubercles; common base of outer and median arms of surstylus short, broad; outer arm trapezoidal, straight lateral sides, broadening apically to twice width at base, apically with row of 17 tubercles (Fig. 150); median arm slender, parallel-sided, slightly curved rod, shorter than outer arm, apically with six setulae, no spinous setae; outer arm and basal half of median arm clothed in microtrichia on outer side; inner arm short, ca. half-length of other arms, with bulbous preapical apophysis; subepandrial clasper elongate, narrow, hardly constricted at base, apical corners rounded, apically hardly convex (Fig. 151); male cercus basally narrow, broadening apically, with broad lateral extension.

Figures 139–145. 

Centrioncus prodiopsis, ♀, Oloitokitok 139 habitus, lateral view 140 thorax, dorsal view 141 head, anterolateral view 142 abdomen, dorsal view 143 fore femur, inner view 144 hind femur, outer view 145 hind femur, inner view. Scale bars: 0.5 mm (139–142); thorax, head, abdomen), 0.2 mm (143–145).

Figures 146–149. 

Centrioncus prodiopsis, ♀, Oloitokitok 146 sternites 1–6, ventral view 147, 148 sternite 7, ventral view 149 tergite 7 and cerci, posterolateral view. Scale bars: 0.5 mm (146); 0.1 mm (147–149).

Feijen (1983) studied the ♂ lectotype and one ♀ paralectotype. The redescription by Hennig (in litt.) of the specimen of the type series in ZMHB also became available. Now two additional females from Kenya could be examined, but one of these two flies was rather teneral. Updated biometrical data are now given. Additional morphological data and illustrations are presented.

Measurements. Speiser (1910) provided length for type series as 4¾–5¼ mm. Length of body 5.9 mm (♀ paralectotype), 4.9 mm (Kenya ♀) and 5.0 mm (♂ lectotype), width of head 1.20 mm (♀ paralectotype), 1.08 and 1.04 (Kenya ♀♀), and 1.06 mm (♂ lectotype), length of wing 5.4 mm (♀ paralectotype), 4.5 mm (Kenya ♀) and 4.6 mm (♂ lectotype), length of scutellar spine 0.37 mm (♀ paralectotype), 0.34 and 0.36 (Kenya ♀♀), and 0.29 mm (♂ lectotype).

Head. As in lectotype and paralectotype, Kenya specimens with frons slightly depressed mesally, anterior quarter of pruinose frons less dark brown and on either side of ocellar tubercle with glossy spot (Fig. 141); length of outer vertical seta 0.31 mm (n = 2), length of fronto-orbital seta 0.22 mm (n = 2).

Thorax. Collar dark brown, mainly glossy; basiliform prosternum dark brown, slender, triangular and anteriorly acuminate; scutum blackish brown and pruinose, humeral callus brown and more glossy (Figs 139–141), Speiser (1910) stated humeral callus dark mahogany red, but was not visible in Feijen (1983); scutellum blackish brown, pruinose, lateral sides and spines brown (Figs 139, 140); colouration of pleura of Kenya specimens corresponds to description of lectotype and paralectotype by Feijen (1983), especially more brownish propleuron with paler ventral half (Fig. 139); densely pruinose spot on katepisternum (also mentioned by Speiser) distinct (Fig. 139); basiliform prosternum dark brown, slender, triangular and anteriorly acuminate; scutellar spine/scutellum ratio: 0.98 (n = 2, range 0.97–1.00); scutellar spine/body length ratio: 0.069 (n = 1); two Kenya specimens with apical seta/scutellar spine ratio: 1.02 (range 1.00–1.04) [Feijen (1983) described apical seta as “slightly larger than spine”]; scutellar length/scutellar width (at base) ratio: 0.64.

Wing. Almost transparent with very large, distinct, brownish central spot covering nearly basal half of cell r4+5 (well past crossvein dm-m), extending into distal half of cell br and extending into distal two-thirds of cell bm+dm and well into cells r2+3, m1 and m4 (Fig. 8); vein CuA+CuP from vein CuP onward extending under angle of 30° to wing margin in almost straight line; vein M4 continuing distal of crossvein dm-m in almost straight line to wing margin; cell cua subtriangular (Fig. 8).

Legs. Femur 1 (Fig. 143) strongly incrassate, l/w ratio: 2.92 (n = 1); two rows of spinous setae on distal two-thirds of femur 1 with 7.3 ± 0.2 setae (n = 8), inner row with 3.9 ± 0.1 setae, outer row with 3.4 ± 0.2 setae; two rows of tubercles on distal three-quarters of femur 1 with 31.1 ± 0.6 tubercles (n = 8), inner row with 15.4 ± 0.3 tubercles, outer row with 15.8 ± 0.4 tubercles; femur 1 yellowish brown with on inner side brown stripe on distal two-fifths (Fig. 143); femur 3 (Fig. 145) distally with 3.9 ± 0.4 (n = 8) tubercles; setal formula 3.4, 3.9, 15.8, 15.4, 3.9 which agrees with formula of type-series as given by Feijen (1983): 3.5, 3.8, 15.8, 14.3, 3.0; femur 3 yellowish with on outer side brown stripe on distal quarter and on inner side vague brown spot apically (Figs 144, 145).

Preabdomen. Tergites uniformly blackish brown (Fig. 142), almost glossy, laterally with some pruinosity (Fig. 139); sternites brownish (Fig. 139); sternite 1 glossy but laterally with some pruinosity, sternite 2 glossy, sternites 3–6 pruinose (Fig. 146); membranous ventral areas with dark lateral spots; sternite 1 trapezoidal, anteriorly broader (Fig. 146); intersternite 1–2 dark, laterally acuminate, with thin lateral connections to main sternite 2; sternite 3 rectangular with rounded corners; sternites 4 and 5 anteriorly rounded, with significant rounded invagination, both sternites with pair of small heavily sclerotised spots anteriorly (Fig. 146); sternite 5 half-length of sternite 4; sternite 6 broadening posteriorly, ~ 1.4× as broad as sternites 1–5, with convex lateral sides.

Female postabdomen. Tergite 7 brown, paler brown along posterior margin (Fig. 149); anterior sclerite of sternite 7 trapezoidal, narrowing posteriorly, w/l ratio: ~ 2.5 (Figs 147, 148, Table 8), brown but paler along posterior margin, glossy on anterior two-thirds, pruinose on posterior one-third; posterior sclerite of sternite 7 rounded, broadly U-shaped (Figs 147, 148), clothed in microtrichia and with 4–6 setulae at both posterior apices; cercus (Fig. 149) rather elongate, l/w ratio: 4.0 (Table 8); 7^th spiracle at edge of tergite (Fig. 148).

Male postabdomen. Outer and median arms of surstylus well separated, with short, broad common base (Fig. 150); outer arm somewhat trapezoidal with straight lateral sides, broadening apically to almost twice width at base, apically with row of 17 tubercles with tiny setulae in between, with rectangular, raised section with 11 setulae basally on inner side (Fig. 150), outer arm wholly clothed with microtrichia on outer side; median arm slender, parallel-sided, slightly curved rod-shaped, slightly shorter than outer arm, apically with 4 small setulae and 2 long setulae, no spinous setae present, basal half of outer side covered with microtrichia; inner arm of surstylus short, ca. half-length of other two arms, with a bulbous preapical apophysis, apically with five setulae (Fig. 150); subepandrial clasper (Fig. 151) elongate, slightly constricted at base, narrow, somewhat rectangular, apically with rounded corners, apical edge slightly convex, glabrous, with three long setulae centrally on inner side and four small hairs at apical edge; cercus basally narrow, broadening apically, with short, broad lateral extension, length/greatest width ratio: 1.4 (Table 8); ejaculatory apodeme + sac very large, 12% of body length (Table 9).

Figures 150, 151. 

Centrioncus prodiopsis, ♂, lectotype, Kibongoto 150 surstylus, inner view 151 subepandrial clasper and base of surstylus, posterior view. Scale bars: 0.1 mm.

The collecting localities are shown on the map for Eastern Africa (Fig. 29). The type locality is on the southern side of the Kilimanjaro region, while the Kenyan specimens are from the northern side of the Kilimanjaro region. In a straight line, the distance between the two localities is 55 km.

Speiser (1910) based his description on two pairs of specimens. Feijen (1983) used for his redescription one pair from NHRS. In the NHRS collection, there was one additional fly without an abdomen, while ZMHB also housed one fly without an abdomen. Feijen designated the ♂ of the pair studied as lectotype and the ♀ as paralectotype. Now, a typed letter from W. Hennig, dated 3.xii.1947, was recovered from the J.F. Shillito archive (NHMUK). The section relevant to Centrioncus ran as follows:

Ueber den Holotypus von Centrioncus prodiopsis Speiser, der sich in der Sammlung des Zoologischen Museums Berlin befindet, habe ich mir früher einmal, für den Fall, dass er zerstört werden sollte, Notizen gemacht. Kopien meiner Zeichnungen fuge ich für Sie diesem Briefe bei. Sie können diese Zeichnungen beliebig verwenden. Auch gegen Veröffentlichung habe ich nichts einzuwenden, da wir hier doch in absehbare Zeit nicht dazu kommen.

Ueber die systematische Stellung von Centrioncus prodiopsis habe ich mir noch kein abschliessendes Urteil gebildet. Ich weiss nur sicher, dass die Art nicht zu den Sepsiden, und auch nicht zu den Megamerinidae gehört. Gegen Ihre Ansicht, dass es sich um eine Diopside handelt, wäre von der morphologie des Kopulationsapparates her wohl kaum etwas einzuwenden. Da ich selbst aber die Verwandtschaftsgruppen um die Sapromyzidae noch nicht genügend untersucht habe, möchte ich mit meinem Urteil vorläufig zurückhalten. Von Kopfborsten sind nur 1 Vertikalborste und 1 Frontorbitalborste vorhanden, von Thorakalborsten 1 Notopleuralborste (die hintere), 1 Supraalar- und 1 Postalarborste.

[In a brief translation this comes to: Regarding the holotype of Centrioncus prodiopsis in ZMHB, I made years ago notes in case it would be destroyed. I enclose copies of the drawings I made. If you like, you can use these for publication. I have not yet formed a conclusive judgment on the systematic position of Centrioncus prodiopsis. I only know for sure that the species does not belong to the Sepsidae or Megamerinidae. In view of the morphology of the copulation apparatus, there would hardly be anything to object to your view that it is a diopsid. However, I would like to reserve my judgment for the time being. On the Centrioncus head 1 vertical seta and 1 fronto-orbital seta are present, while the thorax counts 1 notopleural seta (the posterior one), 1 supra-alar seta and 1 postalar seta.]

From this letter, it became obvious that the fly without abdomen in ZMHB is a male, so the fly without abdomen in NHRS has to be a female. Hennig indicated the ZMHB fly as the holotype. However, Speiser did not designate a holotype. All four specimens of the type series were labelled as syntypes (Feijen 1983). It seems likely that Hennig was not aware of the three NHRS flies. As such, the designation of the lectotype by Feijen (1983) remains valid. Hennig’s drawings of the ZMHB fly showed that this male was definitely conspecific with the lectotype. As, since the type series of 1905–1906, male specimens of C. prodiopsis have apparently never been collected again, it is considered useful to copy Hennig’s drawing of the male postabdomen (Fig. 152) as an addition to Feijen’s (1983) drawings and for historical reasons. In this drawing, Hennig’s original labels are indicated. The ZMHB specimen is now designated as male paralectotype.

Figure 152. 

Centrioncus prodiopsis, ♂, abdomen segments 5–8, epandrium and surstylus, lateral view. This is a (restored) drawing made by Willi Hennig in the late 1930s. Hennig was probably not aware of the three ZMHB specimens and assumed the NHRS specimen to be the holotype. The NHRS specimen is now designated as paralectotype.

Figures 153, 154. 

Ejaculatory apodeme + sac 153 Centrioncus decoronotus, paratype, Chania Falls 154 Teloglabrus sanorum, paratype, Drakensberg. Both drawings were processed based on original pencil drawings from Feijen (1983: figs 115, 126) and are drawn to the same scale. Scale bar: 0.2 mm.

Lonsdale (2013), in a review of Tanypezidae and Strongylophthalmyiidae, includes for the phylogenetic analysis in the character matrix as out-group representatives for the Diopsidae Sphyracephala subbifasciata Fitch and Centrioncus prodiopsis. However, the origin of the single Centrioncus studied was not given, though for the genitalia character states, Feijen (1983) was used. The two specimens from Kenya were, after 106 years, the first C. prodiopsis collected since the type series. Literature references to additional C. prodiopsis records related to other Centrioncus species or to Teloglabrus species (Feijen 1983).