A revision of the genus Teleopsis Rondani (Diptera, Diopsidae) in Sri Lanka with descriptions of two new species and a review of the other stalk-eyed flies from the island

Abstract The literature on Sri Lankan Diopsidae is reviewed. Eight Diopsidae are now known to occur in Sri Lanka, five species in the genus Teleopsis and one species each in the genera Sphyracephala, Diopsis, and Cyrtodiopsis. The presence of Cyrtodiopsis requires confirmation to exclude the possibility of mislabelling. All five Teleopsis species are endemic, as are the Diopsis species and probably the Cyrtodiopsis species. Only Sphyracephala bipunctipennis Senior-White has a larger distribution as it also occurs in India. A key is presented for the Diopsidae of Sri Lanka. Three Teleopsis species were already known to occur in Sri Lanka: T. ferruginea Röder, T. krombeini Feijen and T. maculata Feijen. These species form the T. ferruginea species group. Two new species are now described for this group: Teleopsis neglectasp. nov. and Teleopsis sororasp. nov.Teleopsis ferruginea is redescribed, as an earlier redescription turned out to be based on a series of specimens of its sister species T. sororasp. nov. The other three Diopsidae of Sri Lanka are listed and illustrated. Allometric aspects of the five Teleopsis species are discussed. Three Teleopsis species are sexually dimorphic with regard to eye span, while two species are monomorphic. It is assumed that sexual dimorphism developed independently in the T. ferruginea species group. This brings the number of known cases of independent development of sexual dimorphism in the Diopsidae to ten.


Introduction
Five species and three genera of Diopsidae were known to occur in Sri Lanka (Feijen 1998). The genera Diopsis Linnaeus and Sphyracephala Say were both represented by one species, while Teleopsis Rondani counted three species. An overview will now be given of the rather limited literature on Diopsidae from Sri Lanka. The Teleopsis species in Sri Lanka belong to the Teleopsis ferruginea species group and this group will now be revised, expanding the group to five species. In the collections of NHMUK, two Teleopsis specimens were found which represent an undescribed species. These specimens will here be described as Teleopsis neglecta sp. nov. In the collections of NHMB, two male Teleopsis specimens were found which proved to be conspecific with Teleopsis ferruginea Röder of which the female holotype was fixed by monotypy. Feijen (1998) examined the teneral holotype and gave a redescription of T. ferruginea based on a series of 50 specimens. Comparison of the holotype and the two NHMB males with the series of 50 specimens showed that in fact two closely related species were involved. This issue will now be resolved by redescribing T. ferruginea based on its holotype and the two NHMB males, while as new species Teleopsis sorora sp. nov. will be described based on the series of 50 specimens and some additional specimens. Additional information will also be given for the two other Teleopsis species in Sri Lanka: T. krombeini Feijen and T. maculata Feijen. These species will be illustrated with photographs of the holotype and/or paratype.
In the collection of ZMUO, three specimens of Cyrtodiopsis Frey with Ceylon (Sri Lanka) labels were found. These belong to the Cyrtodiopsis dalmanni species group and would form a remarkable extension of the range of genus and species group. A key will be presented to the eight species now known to occur in Sri Lanka. The three species of the genera Sphyracephala, Cyrtodiopsis and Diopsis will be listed and illustrated. Allometric aspects with regard to the sexual dimorphism of the eye stalks in the Teleopsis ferruginea species group will be discussed. Allometric data will also be presented for the monomorphic Diopsis species.

Material and methods
The description of T. sorora sp. nov. is based on a large series of pinned specimens. For the description of T. neglecta sp. nov. only two pinned specimens in rather poor condition were available, one specimen lacking the abdomen, while a male specimen lacked the head. Fortunately, five photographs of live specimens became available via www.iNaturalist.org. From the same source also photographs for T. krombeini and T. sorora sp. nov. were obtained. The redescription of T. ferruginea (Röder, 1893) is based on the rather teneral female holotype and two pinned male specimens. For the rate of dimorphism D, the difference between males and females in allometric slope for eye span on body length is used in the Diopsidae . Details on procedures for preparing genitalia slides, and procedures for taking measurements are given in Feijen et al. (2018a). For information on morphological terminology and on

Overview of literature on Sri Lankan Diopsidae
The literature on Diopsidae from Sri Lanka is rather limited. The first paper is by Röder (1893) and describes Diopsis ferruginea from southern Sri Lanka (Ceylon meridionalis). Wulp (1896) listed Diopsis ferruginea in his catalogue of Diptera from South Asia. Likewise, Brunetti (1907) listed Diopsis ferruginea in his catalogue of Oriental Diopsidae. In 1922, Senior-White described Teleopsis bipunctipennis from "five males and seven females, all in good condition, and all taken at one sweep of the net on leaf of a plant growing in the water at edge of the Suduganga river". Frey (1928) assumed that Diopsis ferruginea should eventually be placed in Megalabops Frey. Curran (1936) reported Diopsis ferruginea from Mergui, India, which is now in southern Myanmar. However, Shillito (1940) stated that this was a misidentification and that it concerned Cyrtodiopsis currani Shillito. Shillito furthermore considered that Diopsis ferruginea should be placed in Megalabops and Teleopsis bipunctipennis in Pseudodiopsis Hendel. Shillito (1971) maintained these allocations for the two Sri Lanka species. Descamps (1957) mentioned Diopsis ferruginea and Teleopsis bipunctipennis in his catalogue. Steyskal (1972) still listed Teleopsis bipunctipennis as such, while he placed Diopsis ferruginea in Teleopsis. In 1977, Steyskal in his catalogue of Oriental Diopsidae listed Pseudodiopsis bipunctipennis and Teleopsis ferruginea from Ceylon. Feijen (1989) transferred Pseudodiopsis bipunctipennis to Sphyracephala. Feijen (1998) listed five Diopsidae species for Sri Lanka. Sphyracephala bipunctipennis and a Diopsis of the indica species group were dealt with in a key to the diopsids of Sri Lanka and briefly discussed. Teleopsis ferruginea was redescribed, while as new species Teleopsis krombeini and Teleopsis maculata were described. Feijen (2011) placed these three Teleopsis in the Teleopsis ferruginea species group of Sri Lanka and described it as a distinct and aberrant species group in its genus. Feijen & Feijen (2019) indicated T. ferruginea as an endemic species of Sri Lanka, while the T. ferruginea species group was thought to form an isolated group in its genus. Sphyracephala bipunctipennis was reported from Tamil Nadu, India, so it no longer qualified as an endemic species of Sri Lanka.  : Steyskal 1972: Steyskal : 11, 1977Feijen 1998: 55 (record of holotype only, redescription based on "Further material" now referred to Teleopsis sorora sp. nov.).
Head. Central part glossy dark brown, almost black (Figs 2, 3), face laterally with some very fine pollinosity; frons (Figs 2, 3) very smooth, surrounded by simple, semicircular ridge; arcuate groove thin and concolourous; face very smooth, no facial teeth, lateroventral corners rounded, almost bare, a few tiny pale setulae; eye span in holotype ♀ small (19% shorter than body length) and small to medium-sized in the two males (15% shorter than body length in the small male and 1% longer than body length in the large male); probably moderate rate of dimorphism in eye span, comparison of the three data points with the graph for T. sorora sp. nov. (see Fig. 51) indicates a D of around 0.8; stalks brown, broad apical parts blackish, dorsal part of stalks pollinose; inner vertical seta small and setula-like in the ♀, just more than 0.5× the diameter of the stalk, in the two ♂ the inner vertical seta is likely to be broken off, base of inner vertical seta small, just more than 0.1× the stalk diameter; outer vertical seta 1.4× stalk diameter.
Wing. Irrorated with three crossbands (Figs 1, 7); apex (apical 6% of wing) distinctly infuscated, infuscated area linked to preapical band along veins and wing edge; preapical band broad, almost uniformly dark, posteriorly slightly paler, broadly linked to central crossband in cell r4+5, slightly extending into cells r2+3 and m; two clear spots in between the central and preapical bands, one in cells r1 and r2+3, and one basally in cell m1; broad, but irregular central crossband including crossveins r-m and dm-m, darker in cell r1 and around veins R4+5 and M4; irregular basal band narrow, darker in cell r1 and around vein M4, several connections to central band, giving two pale spots in cell br and cell m4, a vague dark stripe running from cell cua to the pale spot in cell m4; cell r4+5 narrower basally and apically; vein M4 from crossvein dm-m onward turning downward and reaching till more than three-quarters of the distance to the wing edge; glabrous basal areas including basal half of cell c, tiny basal spot in cell r1, basal half of cell br, basal quarter of cell bm+dm except for posterior edge, and posterior half of cell cua.
Head. Eye span (Figs 22-24) small in female (78.4 ± 0.7% of body length) and medium-sized in male (96.8 ± 3.3% of body length); a dimorphic species with a moderate rate of dimorphism D = 1.03 (Fig. 28); inner vertical seta small, equal in size to stalk diameter, usually not broken off; base of inner vertical seta small, almost 0.5× the stalk diameter; outer vertical seta medium-sized, about 1.7× the stalk diameter, spinous.
Distribution. Teleopsis krombeini is now known from Kandy District and Matale District, Central Province and Kegalle District, Sabaragamuwa Province. Feijen, 1998 Figures 10, 20, 25, 31-33, 62, 63 Teleopsis maculata Feijen, 1998 two data points for ratio eye span/body length in T. maculata (Figs 62,63) are compared with the data points for the dimorphic T. ferruginea, T. krombeini and T. sorora sp. nov., these two points are in slope similar to the females of the three dimorphic species; inner vertical seta medium-sized, about 1.5× the stalk diameter; base of inner vertical seta small, less than 0.5× the stalk diameter; outer vertical seta medium-sized, about 2.0× the stalk diameter, spinous (Figs 25, 33).
Distribution. Teleopsis maculata is known from the Central Province (Nuwara Eliya district). As the Hakgala Reserve is partly located in Uva Province, it probably also occurs there. Diagnosis. Teleopsis neglecta sp. nov. can be recognised by its slender habitus, bareness, wing pattern (apical 10% vaguely infuscated, three distinct crossbands strongly interconnected giving four distinct pale spots, basal anterior spot not extending into cell bm+dm), wing mostly covered by microtrichia except for most of basal quarter and anterior spots, inner vertical seta and outer vertical seta spinous, tiny base of inner vertical seta, no facial teeth, dorsally glossy collar, reddish brown, thinly pollinose scutum and scutellum, ratio scutellar spine/scutellum ~ 3.1, incrassate front femora with around 54 (♂) tubercles, abdomen dark, large glossy spot laterally on terga 1 and 2, pair of pollinose spots on tergum 3, tergum 4 glossy, tergum 5 densely pollinose, male spiracles 7 symmetrically in synsternum, surstyli articulate, slender, apically rounded, ratio length/width in lateral view 2.5, surstyli without microtrichia, broad male cerci, ratio eye span/body length ~0.60-0.70 in ♂, and assumed sexual monomorphism with regard to eye span.
Teleopsis neglecta sp. nov. forms part of the T. ferruginea species group. Like T. maculata, it is more distant from the dimorphic species in this group (T. ferruginea, T. krombeini and T. sorora sp. nov.), also given the differences in the male synster- num. However, for an understanding of the phylogenetic relationship between T. neglecta sp. nov. and T. maculata more information has to become available (morphology of female genitalia, molecular analyses and wing geometric morphometrics analyses).
Head. Central part yellowish brown (Figs 34-37), thinly pollinose; frons (Fig.  37), smooth, with a shallow dimple in front of ocellar tubercle; arcuate groove dark brown; face smooth, slightly bulging centrally, no facial teeth, lateroventral corners rounded, bare, no setulae; eye span probably very small, in holotype estimated as ~60% of the body length (based on comparison of measurements of holotype and paratype), from the photograph of a live specimen an estimate of ~70% of body length is made; the rate of dimorphism in eye span cannot be estimated from the few data available, but it seems quite certain that T. neglecta sp. nov. is a monomorphic species; although no females are available, the very small eye span in the holotype forms a clear indication that this is a monomorphic species; when the data point for ratio eye span/body length in T. maculata (Figs 62, 63) is compared with the data points for the dimorphic T. ferruginea, T. krombeini, and T. sorora sp. nov., this point is similar to those for the females of the three dimorphic species [measurements are, like for T. maculata falling in the range for the monomorphic genus Megalabops]; stalks brown, broad apical parts blackish, thinly pollinose; inner vertical seta tiny, 0.1× the diameter of the eye stalk (Fig. 36), base of inner vertical seta small, 0.2× the stalk diameter; outer vertical seta broken off, but spinous (distinct in live photograph, Figs 34, 35).
Wing. Irrorated with three distinct crossbands (Figs 11,34,35); apical 10% of wing uniformly vaguely infuscated; preapical band broad and dark, posterior half slightly paler, broadly linked to central crossband in cell r4+5, slightly extending into cells r2+3 and m; two clear spots in between the central and preapical bands, one in cells r1 and r2+3, and one basally in cell m1; central crossband dark and almost as wide as preapical band, including crossveins r-m and dm-m, darker veins R4+5 and M4, slightly less dark on posterior half, preapical and central crossband together forming a solid H-configuration; basal band dark and half the width of the other bands, darker around vein M4 and posteriorly of cell cua, a strong connection to central band in cell bm+ dm and around vein M4, giving two pale spots, one in cells r1 and br and the other centrally in cell m4; cell r4+5 narrower basally and apically; vein M4 from crossvein dm-m onward turning slightly downward and reaching till just more than half the distance to the wing edge; glabrous basal areas including most of cell c except for apex, posterior basal sixth of cell r1, basal half of cell br, basal fifth of cell bm+dm except for posterior edge, and most of cell cua except for apex and anterior margin; anterior spots also almost bare.
Legs. Front leg yellowish brown pollinose (darker in live flies), femur with very vague brown stripe on inner side, tibia darker brown; mid leg brown, femur with dark brown stripes on distal half; hind leg brown, femur with dark brown stripe on whole length, hind tibia darker brown; femur 1 ( Fig. 39) incrassate in paratype, ratio of length/width 3.9, tubercles on distal three-quarters of ventral side, inner row in paratype with 28 tubercles (N = 1), outer row with 26 tubercles.
Head. Central part glossy black (Figs 27, 48-50), face laterally and ventrally covered with a typical, 'woolly' type of pollinosity, face and frons otherwise bare with only a few tiny pale setulae; frons (Fig. 27) very smooth with laterally at base of stalk a deep groove; arcuate groove narrow and concolourous; face flat and very smooth, facial sulcus indistinct, no facial teeth, lateroventral corners rounded; mouthparts greyish brown; eye span small in female (78.6 ± 0.9% of body length) and medium-sized in male (99.4 ± 1.5% of body length); a dimorphic species with a low rate of dimorphism D = 0.82 (Fig. 51); stalks yellowish brown, anteriorly and posteriorly with a blackish band, apices blackish pollinose; inner vertical seta usually appears minute, 0.1× the diameter of the eye stalk, in a single teneral specimen there is a small, setula-like inner vertical seta of 0.6× the stalk diameter (these slender inner vertical seta probably drop off early in the life of the fly); base of inner vertical seta small, just more than 0.2× the stalk diameter; outer vertical seta medium-sized, about 1.8× the stalk diameter, spinous.
Wing. Irrorated with a dominant, dark, curved preapical band (Figs 8, 50) and, in addition, two very indistinct crossbands; apex (apical 12% of wing) infuscated, slightly less infuscated area centrally near preapical band; preapical band broad, curved, apically convex, proximally concave, uniformly very dark, broadly linked to central crossband in and around cell r4+5; two pale spots in between the central and preapical bands, one in cells r1 and r2+3, and one basally in cell m1; broad, but vague and irregular central crossband including crossveins r-m and dm-m, slightly darker around vein M4; narrow, indistinct and irregular basal band, connections to central band, giving two pale spots, one distally in cell br and one centrally in cell m4; cell r4+5 narrowing subapically; vein M4 from crossvein dm-m onward turning downward and reaching till three-fifth of the distance to the wing edge; glabrous basal areas including basal half of cell c, tiny spot basally in cell r1, central quarter of cell br, basal third of cell bm+dm except for edges, and posterior half of cell cua. The two pale wing spots proximally of the dark preapical band clearly coincide with the pair of whitish, densely pollinose spots adjoining the black apical section of the abdomen (Figs 48-50, especially Fig. 49). The same phenomenon was observed in the sister species T. ferruginea (Feijen 1998). Coinciding wing spots and abdominal spots are a common phenomenon in several Diopsidae genera.
Distribution. The specimens of the type series are from three neighbouring locations in Kandy: Udawattakele Sanctuary, Darwin Reservoir and Roseneath. If the NHMUK specimens also represent T. sorora sp. nov., this would extend the known distribution to the surroundings of Colombo and the wider surroundings of Kandy. Etymology. This new species is considered the sister species of Teleopsis ferruginea, hence the name sorora (sister).

Discussion
The biogeographic range of Teleopsis Feijen and Feijen (2011) discussed the biogeographic range of the genus Teleopsis. They indicated Teleopsis s. s. as a purely Oriental genus with species occurring in India, ? Myanmar, Sri Lanka, Indonesia (Sumatra, Java, Bali and Borneo only), Malaysia, Brunei, Thailand, China (only Hainan), and the Philippines. For the second Diopsidae genus with supra-alar spines, Megalabops Frey, they gave a more northern distribution with species in occurring in Nepal, Northern India, Myanmar, West Malaysia, Thailand, Cambodia, Vietnam, and China (mainland and Taiwan). To the range for Teleopsis can now be added Vietnam and Southern Mainland China (Yunnan), while to the range of Megalabops can be added Bhutan (see Feijen and Feijen 2019) and Laos. Feijen and Feijen (2019) discussed the Teleopsis species groups in India and Sri Lanka. The Indian and Sri Lankan Teleopsis form isolated groups in their genus from morphological as well as geographical point of view. In India, only the Teleopsis sykesii species group occurs with its two species distributed in Western India. From Eastern India, Teleopsis are not known, so the T. sykesii group forms an isolated group. The Teleopsis species geographically closest to the T. sykesii group are found in Sri Lanka. They belong to the equally isolated T. ferruginea species group. Otherwise the nearest Teleopsis members are found in Thailand and Peninsular Malaysia. The two T. sykesii records for Myanmar are very doubtful . Molecular data for India and Sri Lankan Teleopsis are still lacking, but a close relationship between the two species groups appears unlikely.

The Teleopsis ferruginea species group
For the phylogenetic position of Teleopsis within the Diopsidae can be referred to Feijen et al. (2018a). Teleopsis forms part of the Teleopsis genus group, characterised by irrorated wings. Within Teleopsis, the species of the T. ferruginea group can be characterised by their bareness, small to medium-sized inner vertical seta (0.5-1.5× stalk diameter), tiny to small base of inner vertical seta (0.1-0.5× stalk diameter), absence of facial teeth, moderately incrassate to incrassate front femora (mean ratio length/ width varying from 3.8-4.9), male sternum 5 consisting of two sclerites, indiscernible male sternum 6, small and articulating surstyli with 10-25 setulae and without microtrichia, and ribbon-like male synsternum with 7 th spiracles in sclerite or in lateral slit of sclerite. Female genitalia have only been described for T. krombeini and T. sorora sp. nov. Based on only these two species, additional character states of the T. ferruginea group might be: ♀ tergum 7 and sternum 7 unconnected, ♀ spiracles 7 in membrane, and spermathecae with very short tubercles.
Within the species group, T. ferruginea, T. sorora sp. nov., and T. krombeini form a subgroup based on similarities in shape and setulae of the surstylus, the lateral slit in the male synsternum accommodating left spiracle 7, the sexual dimorphism with regard to eye span and the similar allometric slope for male eye span on body length. Teleopsis ferruginea and T. sorora sp. nov. are obvious sister species based on shape and colouration of central head, colour pattern of scutum and dorsal abdomen and male genitalia. The sexually monomorphic T. neglecta sp. nov. and T. maculata stand separate from the three dimorphic species, given also that in both species the left male spiracle 7 is located in sclerite. However, as indicated above, more information is required to determine the relationships between T. neglecta sp. nov. and T. maculata and with the group of dimorphic species.
Dimorphism and monomorphism in the Sri Lankan Teleopsis , comparing allometric data with a phylogenetic tree based on molecular analyses, concluded that for the Diopsidae "Sexual dimorphism in eye span has evolved independently at least four times in the family ...". Later, Feijen and Feijen (2014) and F.A.A. Feijen (pers. obs.) found that there were, at least, eight cases of independent development of sexual dimorphism with regard to eye span within the Diopsidae. This concerned three cases in the Sphyracephalinae, one in the Diasemopsis genus group, at least three in the Teleopsis genus group (the irrorated wings group) and one in the genus Diopsis. The dimorphic Malagasy Diopsis nigrosicus, distantly related to the monomorphic Diopsis ichneumonea species group of African Mainland, provided the ninth case (Feijen et al. 2018b). The five Sri Lankan Teleopsis species can, based on morphological criteria, be assumed to belong to the monophyletic Teleopsis ferruginea species group. Within this species group there are three distinctly dimorphic species: T. ferruginea, T. krombeini, and T. sorora sp. nov. For the other two species, T. maculata and T. neglecta sp. nov., only a few specimens are available, but they can, in all likelihood, be assumed to represent monomorphic species. As such the number of cases of independent development of sexual dimorphism with regard to eye span now comes to ten.

Other Diopsidae in Sri Lanka
Notes. The three other Diopsidae known from Sri Lanka are Sphyracephala bipunctipennis, Cyrtodiopsis sp. and Diopsis sp. For descriptions of the latter two species, large scale revisions will be required for, respectively, the Cyrtodiopsis dalmanni species group and the Diopsis indica species group. Here, the collecting data are given for the three species concerned. For all three species illustrations are provided for the habitus (Figs 64, 67,  70), the anterior view of the head (Figs 65, 68, 71) and the wing (Figs 66, 69, 72). As a very large sample of flies was available for the Diopsis sp., its monomorphism with regard to eye span, will briefly be discussed.
Notes. This species forms part of the Cyrtodiopsis dalmanni species group. The presence of Cyrtodiopsis in Sri Lanka would be rather surprising, given that the nearest relatives in the C. dalmanni group occur in Malaya and Indonesia. The geographically closest Cyrtodiopsis is C. whitei Curran from north-eastern India. However, that species belongs to a different species group. The Sri Lankan record certainly requires confirmation to exclude the possibility of mislabelling.
Although many non-taxonomic papers have been written about "Cyrtodiopsis dalmanni", the taxonomy of this species and the C. dalmanni species group still requires a full-scale taxonomic revision. This species group can be characterized by the many, long setulae covering the body, the wing pattern with three pale spots in between the central and preapical crossbands and the peculiar peg and hollow modification on the male front leg, the peg located basally on the tibia and the hollow distally on the femur. This leg modification is also referred to as "nutcracker" and can be found in all males, except for small ones. For illustrations of this modification can be referred to Földvári et al. (2019: fig. 4).  Notes. The large Girandurakotte sample of 276 flies, collected by a UV trap, is quite remarkable. We are not aware of any other substantial collection of Diopsidae by this type of trap. Although this Diopsis of the D. indica species group definitely represents a new species, its description has to await designation of a neotype for D. indica and a full revision of the species group it belongs to. The group counts more than 20 undescribed Oriental species. For more information on this group can be referred to Feijen (2009, 2019).
Sexual monomorphism. As has already been indicated in Feijen and Feijen (2019), all species in the D. indica group are sexually monomorphic with regard to eye span. As a large sample of the Sri Lankan species was available, the opportunity was taken to measure 40 ♀ and 40 ♂ to demonstrate the monomorphism in this species group (Fig. 73). The slopes of the allometric lines are almost similar for males and females: respectively 0.88 ± SE 0.06 and 0.93 ± 0.04. The difference gives a rate of dimorphism D of -0.05 and indicates, as such, a sexually monomorphic species. The intercepts show a small difference. There are monomorphic Diopsidae taxa, like Megalabops, where the allometric lines fully coincide, but in others a difference in intercept occurs. This depends on differences in the shape of the abdomen, like rate of deflexion in males.