Research Article |
Corresponding author: Peter Schüle ( sei.schuele@gmx.de ) Academic editor: James Liebherr
© 2021 Peter Schüle, Alexander Putchkov, Tetiana Markina.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Schüle P, Putchkov A, Markina T (2021) Larval descriptions of three Dromica species with some bionomical remarks (Coleoptera, Cicindelidae). In: Spence J, Casale A, Assmann T, Liebherr JК, Penev L (Eds) Systematic Zoology and Biodiversity Science: A tribute to Terry Erwin (1940-2020). ZooKeys 1044: 511-525. https://doi.org/10.3897/zookeys.1044.61993
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Larvae of all instars of Dromica (s. str.) kolbei (W. Horn, 1897), D. (s. str.) alboclavata Dokhtouroff, 1883 and instar I of D. (s. str.) helleri (W. Horn, 1897) are described and figured in detail. The larvae of these species have several unique morphological characters. The shape of the pronotum, appendages of abdominal segment V and the peculiarities of chaetotaxy are of taxonomic importance. The main diagnostic characters to separate these species from each other and from other known Dromica larvae are given and discussed. Some bionomical peculiarities of D. (s. str.) kolbei are presented.
Diagnostic remarks, ecology, morphology, South Africa, Tiger beetle larvae
The genus Dromica was established as a monotypic genus for the species Dromica coarctata (Dejean, 1826) originally described as Cicindela coarctata Dejean in Latreille and Dejean, 1822. The two genera Myrmecoptera Germar, 1843 and Cosmema Boheman, 1848, initially described as distinct genera, have subsequently been regarded as synonyms of the genus Dromica (
In contrast to adults, information about the larvae is very scarce and larval stages of only two species have been described until now (
This work comprises the descriptions of three species belonging to two different “species groups” of the subgenus Dromica (s. str.): D. alboclavata Dokhtouroff, 1883 (group “coarctata / furcata / marginella”), D. kolbei (W. Horn, 1897), and D. helleri (W. Horn, 1897) (group “sexmaculata”).
The descriptions are based on the following larval material:
Dromica kolbei (3 LI, 7 LII, 6 LIII), South Africa, RSA, Northern Province, Ben Lavin Nature Reserve near Louis Trichardt, open bushfield area, 29 Jan 2000, leg. P. Schüle;
Dromica helleri (1 LI), South Africa, Eswatini [Swaziland], Mlawula NR, 22 Nov 2001, leg. P. Schüle;
D. alboclavata (3 LI; 3 LII; 1 LIII), South Africa, RSA, Gauteng, Hartbeestpoort, 5 Dec 2004, leg. P. Schüle.
The larvae were reared ex ovo in laboratory conditions. The nomenclature follows
HL head length (from nasale apex to the end of fronto-clypeal-labral area);
HW head width measured at its broadest portion, usually at the level of stemmata I–II;
PNL pronotum length measured along midline;
PNW pronotum width measured at its broadest portion, usually at level of cephalolateral angles or slightly below;
A1, A2 first and second antennal segments;
LP1 first labial palpus;
LP2 second labial palpus;
ST1, ST2 first and second stemmata;
PN pronotum;
PN1 half of pronotum with number of discal setae (but without marginal setae);
PNa cephalolateral (anterior) angles of pronotum;
PNm median line of pronotum;
T3 third abdominal tergite;
HY hypopleuron,
AT5 apical tergite;
CT5 caudal tergite;
CTL5 lateral tergite of abdominal segment V (hump);
MH medial hook;
IH inner hook on abdominal segment V;
EU9 posterior part of abdominal sternite IX;
TE9 posterior part of abdominal tergite IX;
PY pygopod.
Projections of MH and IH of abdominal segment V are figured in dorsal and partly in lateral views. Length of hooks are measured from the posterior margin at base to the apex of hooks (diagonally). The sizes are given in mm. All larval material is deposited in the entomological collections of Schmalhausen Institute of Zoology NAS of Ukraine (
Measurements: FL 1.70–1.90 (1.80); FW 2.80–3.15 (3.01); PNL 2.05–2.25 (2.14); PNW 3.40–3.75 (3.59). Head. Disk of head posteriorly light brown, almost yellow on anterior third. Remainder of head dark brown with bright greenish blue luster. Ventral side of head dark brown. Most setae of head dark brown or almost black, not flattened. Only some setae on anterior part of clypeus brown or light brown. Mandibles and stipes of maxillae dark brown. Galea light brown. A1 and A2 yellow (or slightly reddish), A3 and A4 brown. Adnasalia distinct and not shorter than lateral teeth (Fig.
Morphological features of Dromica kolbei larvae A pronotum, III instar (right half, above) B pronotum, I instar (right half, above) C hump, III instar (left part, dorsal view) D the same (lateral view) E segment IX and pygopod of abdomen, III instar (dorsal view) F segment IX and pygopod of abdomen, III instar (ventral view).
Measurements: FL 1.17–1.19; FW 2.00–2.20; PNL 1.35–1.40; PNW 2.05–2.08. Differing from instar III mainly by number of setae on some appendages and sclerites. Head. Coloration of head and pronotum same as in instar III but less bright. Most setae on head transparently white and only brown near eyes; A1 with five setae (three on anterior lateral margin). A2 apically with five long setae; A3 with two long, and A4 with two or three long and 4–6 small setae. Galea slightly shorter than maxillary palpus. LP1 with six spinelets, LP2 with one seta slightly before the middle. Epicranial suture absent.
Thorax. PN 1.48–1.52 × wider than long. Anterior margin of PN almost even or slightly concave. Most setae of PN1 slightly flattened and truncated (in instar III: thin and acuminate). Anterior margin of PN with 24–27, PN1 with 8–11 and swellings of PNa with one or two setae. Abdomen Sclerotized areas of abdomen indistinct. T3 with 8–10 setae, HY consisting of one large posterior and one small anterior sclerite. CTL5 with four long setae. Anterior part of CT5 with 12–16 stout bristles and some thin setae. Central spine of IH longer than lateral bristles. EU9 with six long setae. PY with 8–10 setae dorsally and six or seven setae ventrally. Apex of PY with 16 setae (8–10 of them stouter).
Measurements: FL 0.8; FW 1.35; PNL 0.95; PNW 1.50. Head. Anterior third of head light yellow, clypeus brown, lateral margin of head (near eyes) dark brown with greenish metallic luster. All setae of head transparently reddish, slightly flattened and truncated. Apexes of lateral plates near adnasalia shortened, slightly rounded. Tubercles between ST1 and ST2 with one seta. A1 glabrous; A2 and A3 with two long setae; A4 with three long and several small setae on apex. Galea shorter than maxillary palpus. LP1 with three spinelets; LP2 with one seta before middle. Thorax. PN light brown, PNA almost yellow. PN 1.58 × wider than long. Tips of discal setae of PN slightly obtuse. Maximum width of PN in the middle. Anterior margin of PN almost even, longer than widened and rounded tops of PNa (Fig.
Morphological features of Dromica larvae, I instar A hump of D. kolbei (right part, dorsal view) B segment IX and pygopod of abdomen of D. kolbei (left half, dorsal view) C segment IX and pygopod of abdomen of D. kolbei (left half, ventral view) D pronotum of D. helleri (right half, above) E hump of D. helleri (right part, dorsal view) F pronotum of D. alboclavata (right half, above) G hump of D. alboclavata.
Dromica kolbei is distributed in northern South Africa and in southern Zimbabwe. The single record from Angola still needs to be confirmed (
In early February 2000, two adults of D. kolbei were brought back alive to the laboratory in Germany, where they were placed in an open bowl (40 cm × 50 cm × 14 cm) filled with 8 cm of loamy sand, and lit by a 12 V 50 W light bulb 12 hours per day.
The first copulation could be observed during the second day and took only a few minutes, just as all the subsequent copulations. After a few days, the female refused further mating activities by the male. Even if the male’s mandibles successfully gripped the female between the thorax and the elytra (the coupling sulcus being marked by a longitudinal shallow impression on the upper half of the mesepisternum), the male did not succeed in inserting its fully protruding aedeagus. By arrhythmic waggling of the abdomen, the female tried to get rid of the male.
While mating, the male spread out the prolegs, tightly holding the female with its mandibles. The male’s labial palpi, with second palpomeres inflated, flattened and with rows of long setae on the upper surface, were folded backwards and pressed onto the female’s elytra. The use of the male’s dilated protarsi, bearing brush-like adhesive hairs, could not be observed.
Egg laying only took place immediately after watering the substrate. Initially, the female tested the substrate by touching the surface with its palpi, lowering its head while walking slowly. After the female made a small hole by digging with its abdomen, most probably by using its cerci as tools. The abdomen was placed into this hole up to the penultimate tergite, while the ovipositor was extended for ca. 8–10 mm for egg laying.
The first eggs were laid on 6 March. The egg-laying period lasted until the female’s death on 9 June 2000 (95 days later). During this period, the female dug ca. 150 holes. When the female was disturbed by the male, she stopped laying eggs and moved to another area; therefore many holes did not contain any eggs. Furthermore, no larvae left the burrows that had been dug at the end of the egg-laying period.
After hatching, the coiled larvae remained in a small cavity for a few days before digging a circular tunnel to the substrate surface. During the 1st larval instar, the opening of this tunnel was simply rounded. In front of the oblique tunnel opening, the 2nd and 3rd instar dug a transverse cavity, which was larger for the 3rd instar. Sometimes, the tunnel opening was located at the hollowed lateral wall instead of its top. Approximately seventy larvae hatched from eggs and ca. 40 larvae reached the 3rd larval instar (fifteen larvae were killed and added to the second author´s collection). The first larvae could be observed 33 days after the beginning of the egg-laying period. The shortest period between the first instar I larva and the appearance of the instar II larva numbered 21 days while there were 49 days between the first appearance of an instar II larva and the appearance of the instar III larva. After several months, all the instar sizes could be found. In January 2001, seven months after the last eggs had been laid, one specimen of instar I appeared at the surface. In January 2003, the last living instar I larva of the first generation was dug out, 31 months after the last eggs had been laid.
The first pupa was discovered at the beginning of August 2001. The position of the pupa was vertical in a simple cave ca. 1 cm underneath the surface. The first imago of the first generation appeared in September 2001. Several pupae were dug up and placed in a humid box. The hatching of one male was observed: it took ca. 10 hours from the beginning until the elytra were fully developed and another two days for the full coloration to develop. This specimen lived from 31 August to 28 October 2001.
One female was dug up fully developed on the 31 of August. This female started with egg laying 7 weeks later, on 19 October but died on 2 February, after having lived for 5 months. Two eggs with fully developed larvae inside and belonging to the F2 generation were dug up on 6 February. The F2 generation egg mortality was very high, although dozens of eggs were laid, not a single larva hatched.
Measurements: FL – 0.85; FW – 1.48; PNL – 0.95; PNW – 1.58. Head. Head and appendages light brown (only A3 and A4 are darkened). Most setae on clypeus transparently white with reddish hue, setae of occiput (especially near eyes) dark brown. Lateral part of head (near eyes) brown with slight metallic luster. Most setae of head thin and acuminate, (only some setae apically slightly flattened). Outer margin of lateral plates of clypeus slightly curved. A1 glabrous, A2 and A3 with two setae, A4 with two long and several short setae on apex. Galea distinctly shorter than maxillary palpus. LP1 with three bristles; LP2 with one seta before middle. Epicranial suture absent.
Thorax. Disk of PN brown, PNa light yellow. Setae of PN1 dark brown (but lateral and posterior setae transparent white). PN 1.66 × wider than long. Anterior margin of PN almost even, slightly longer than small apices of PNa (Fig.
Dromica helleri is recorded from the Republic of South Africa, Mozambique, and Eswatini [Swaziland] (
Measurements: FL 1.30; FW 2.25; PNL 1.48; PNW 2.58. Head. Dark brown above, sometimes almost black, with greenish copper metallic luster. Ventral side of head light brown medially, lateral portions brown. Mandibles dark brown (more darkened apically). Other appendages of head light brown except A3-4 darkened dark brown. Setae of head’s capsule and A1 transparently white, on A2–4 dark brown. Setae of maxillae and labium light brown. Most setae thin and acuminate, only a few setae near ST1 slightly flattened and truncated apically. Lateral plates of clypeus short, almost rectangular. Tubercles between ST1 and ST2 small, but distinct. Lateral portions of head (below eyes) without distinct tubercles. Maximum width of head on level ST1. Antennae relatively large; A1 1.30 time wider than A2 and 2.0–2.6 × wider than A3, A4. A1 slightly longer than A2 and almost 2 × wider than A3 and A4. A1 slightly flattened dorsoventrally on anterior margin and with 6–7 setae (five of them on median part). A2 with five setae on apical part. Ratios of lengths A1:A2:A3:A4 = 1.0:0.9:0.5:0.6. Maxillary palpus distinctly longer than galea. LP2 not shorter than LP1. Seta on LP2 situated slightly before middle. Epicranial suture absent. Thorax. PN yellow brown on anterior portions, PNa slightly darkened. Setae transparently white (except 10–13 black setae on anterior margin and near PNa). Callous elevations and swellings of PNa not highly elevated but distinct. Maximum width of PN before middle (Fig.
Morphological features of Dromica alboclavata larvae A pronotum, III instar (right half, above) B hump, III instar (right part, dorsal view) C hump, II instar (right part, dorsal view) D segment IX and pygopod of abdomen, III instar (dorsal view) E segment IX and pygopod of abdomen, II instar (left half, dorsal view) F segment IX and pygopod of abdomen, II instar (left half, ventral view).
Measurements: FL – 0.93–0.95 (0.94); FW – 1.50–1.60 (1.53); PNL – 1.00–1.05 (1.02); PNW – 1.63–1.75 (1.68). Head. Dark brown with bright greenish metallic reflection. Appendages brown or light brown. Setae of head capsule white and transparently white. Setae of A2–4 and other appendages brown or light brown (in A1 sometimes white with brown hue). Nasale long, distinctly trapezoid. Adnasalia small. Lateral teeth relatively wide. Tubercles between ST1 and ST2 distinct. Most setae of head acute but some of them (near eyes) flattened and obtuse on top. A1 with three or four setae on anterior side. A2 with four or five setae on dorsal half. A3 with two, A4 with three long and several short setae. Maxillary palpus slightly longer than galea. LP1 with five or six spinelets (three median ones very short). LP2 with one seta slightly before middle. Epicranial suture distinct but short. Thorax. PN light brown without metallic luster. Posterior half of PN light brown. Anterior half and lateral margins of PN light yellow. Most setae of PN white except 10–12 dark brown setae on anterior margin. Tips of PNa with flattened and obtuse setae. Other setae acuminate. Anterior margin of PN slightly concave and longer than PNa. Maximum width of PN in the middle. Callous elevations and swellings of PNa indistinct. PN1 with eight or nine, swellings of PNa with one (rarely two) setae. Legs dorsally light brown, ventrally almost yellow. Abdomen. Sclerotized areas of abdomen indistinct. T3 with seven or eight light brown setae. HY consisting of one large posterior and one small anterior sclerite. Tergites of hump not connected. CT5 with seven or eight stout and 4–6 thin setae (Fig.
Measurements: FL – 0.57–0.65 (0.60); FW – 0.90–1.04 (0.98); PNL – 0.57–0.65 (0.61); PNW – 0.90–1.07 (0.99). Head. Dark brown with greenish luster. Setae transparently white. Lateral teeth of clypeus shorter, lateral margin of adnasalia slightly curved. Setae on clypeus thin and acuminate, setae near eyes distinctly flattened and truncated. Epicranial suture short. Thorax. PN light brown or brown with slight metallic luster. PN 1.38 × wider than long. Maximum width of PN shortly before apex of PNa. Anterior margin of PN almost straight in the middle (sometimes slightly concave) and longer than rounded apices of PNa (Fig.
Dromica alboclavata is a South African species which range is restricted to the Northern parts of the country (
The larvae of Dromica instars II and III can be distinguished from those of other genera of the Prothymina complex by the following characters: MH comparatively shortened, basally distinctly widened with curved apices; two short stout spines of MH are situated one after the other; sclerotized areas of abdomen are indistinct or slightly distinct; CT5 with less than 17 spine-like setae (usually 8–13); PNa small and short; PN1 with 9–13 setae; luster on PN indistinct or moderately distinct. All larvae of Dromica, described here and in earlier papers (Arndt, 1998;
Larvae of instars I of Dromica also show some specific morphological features. CT5 of the known larvae of instar I of the subgenus Pseudodromica is glabrous (
Nevertheless, some other characters (form and chaetotaxy of the head, pronotum, hooks, pygopod) are often similar (or overlapping) in all so far known larvae of Dromica species (Table
Measurements of head and pronotum with growth ratio of pronotal width/length of Dromica larvae.
Species | Instars | Measurements in mm, mean in parentheses | ||||
---|---|---|---|---|---|---|
FL | FW | PNL | PNW | PNW/ PNL | ||
D. clathrata | I | 1.25–1.38 (1.29) | 2.05–2.23 (2.14) | 1.18–1.23 (1.20) | 2.08–2.13 (2.12) | 1.73–1.76 |
II | 1.70 | 3.20 | 1.90 | 3.01 | 1.58 | |
III | 2.50–2.70 (2.57) | 4.00–4.40 (4.20) | 2.70–2.90 (2.83) | 4.40–4.75 (4.55) | 1.62–1.64 | |
D. tuberculata | I | 1.05 | 1.80 | 1.05 | 1.85 | 1.76 |
II | 1.40–1.50 | 2.43–2.63 | 1.55–1.73 | 2.65–2.85 | 1. 65–1.70 | |
D. kolbei | I | 0.8 | 1.35 | 0.95 | 1.50 | 1.58 |
II | 1.17–1.19 | 2.00–2.20 | 1.35–1.40 | 2.05–2.08 | 1,48–1,52 | |
III | 1.70–1.90 (1.80) | 2.80–3.15 (3.01) | 2.05–2.25 (2.14) | 3.40–3.75 (3.59) | 1.66–1.68 | |
D. alboclavata | I | 0.57–0.65 (0.60) | 0.90–1.04 (0.98) | 0.57–0.65 (0.61) | 0.90–1.07 (0.99) | 1.38 |
II | 0.93–0.95 (0.94) | 1.50–1.60 (1.53) | 1.00–1.05 (1.02) | 1.63–1.75 (1.68) | 1.64–1.67 | |
III | 1.30 | 2.25 | 1.48 | 2.58 | 1.75 | |
D. helleri | I | 0.85 | 1.48 | 0.95 | 1.58 | 1.66 |
We dedicate this article to the memory of the famous coleopterologist Dr. Terry Erwin.
We are very grateful to Lutz Behne (Senckenberg Deutsches Entomologisches Institut, Müncheberg), Michael and Amran Balke (Zoologische Staatssammlung, Munich) and Thierry Deuve (Muséum national d´histoire naturelle, Paris) for their assistance during the second author’s visits to the respective museums, and for loans of type specimens and additional material. We thank Andreas Oesterle (Leutenbach) for providing information about rearing Cicindelidae larvae and François Génier (Gatineau, Canada) for revising the English text.