Litoleptis Chillcott, 1186

Kerr, Peter H., 2010, 2592, Zootaxa 2592, pp. 1-133 : 90-91

Genus Litoleptis Chillcott

Figs. 11–12, 50–51, 74, 96.

Litoleptis Chillcott 1963: 1186 . Type species Litoleptis alaskensis Chillcott 1963 , by original designation.

Diagnosis. Several autapomorphic features support the monophyly of Litoleptis . The wing lacks the medial crossvein (so that the discal cell is absent); all tibiae are without spurs; the male aedeagus is very weakly developed, lacking an ejeculatory apodeme; and the gonocoxal apodemes are also absent. Unfortunately, the female terminalia have not been described in the literature and I have been unable to examine any females personally, so these characters remain unknown and its phylogenetic placement remains uncertain.

Litoleptis is composed of species that are small (1.8–2.7 mm); black in color; with hyaline wings; dichoptic eyes in the male; antenna bearing a single, elongated, tapering flagellomere; bare laterotergite; discal cell and M 3 absent; and tibial spur formula of 0:0:0. This genus also shows an unusual disjunct distribution; Litoleptis species are found in Alaska, Chile, China, and the Philippines. This is among the most distinctive of rhagioniform Diptera , however it is most likely to be confused with Hilarimorpha , an asiloid either placed in its own family, Hilarimorphidae . Litoleptis differs from Hilarimorpha in having a pulvilliform empodium; antenna bearing a single, tapering flagellomere; and R 5 and R 4+5 subequal in length. Litoleptis may also be confused with Spania on account of its similar size and the shape of its antenna. Litoleptis may be distinguished from other small flies within Tabanomorpha , such as Bolbomyia and Spania , by the absence of the discal cell, dorsal surface of wing membrane bare, lack of tibial spurs, and males dichoptic.

Description. Head. Clypeus slightly bulbous. Pedicel clearly larger than scape. First flagellomere laterally compressed or rounded in cross section. First flagellomere of antenna elongate as long tapering segment or oval and enlarged near base, with straight, tapering stylus. Eyes inconspicuously setulose; in male, dichoptic (but not widely separated), not flattened dorsally, ommatidia split into dorsal and ventral areas and smaller ventrally. Labella without pseudotracheae, about as long as palpus. Theca short and stout. Palpus onesegmented. Tentorium low on face. Mandibles absent. Cibarial pump long, narrow (clearly not as wide as long).

Thorax. Mesonotum without vittae. Anepisternum bare. Laterotergite bare. Postspiracular scale absent. Proscutellum absent. Subscutellum not enlarged nor lengthened; inconspicuous. Wing hyaline, without markings, without pterostigma. Lower calypter reduced. Upper calypter triangular in form, underdeveloped. Upper calypter with broad curvature, lobe-like, width twice length or less. Costa stops before wing tip or extends past wing tip. Humeral crossvein weakly developed. Sc-r crossvein present, well developed, positioned at proximal side of h by less than length of h. All wing veins and cells bare. R 2+3 sinuous, apical third of R 2+3 ultimately bends anteriorly slightly, toward leading edge of wing margin; longer than R 5, but less than twice as long. Base of R 4 –R 5 fork distal of distal end of cell dm. R 4 at base nearly straight entire length. R 5 anterior to, posterior to, or ending at wing tip; about as long as R 4+5 (r-m to R 4 origin). M 3 wing vein absent. Mcu crossvein absent. Discal cell absent. CuA 2 greater than 2/3 length of posterior vein of cell bm. CuA 2 does not reach wing margin. Alula reduced, without curvature or with narrow curvature. Alula full, rounded evenly. Anal lobe well developed. Halter knob between 1/2–2/3 length of stem. Tibial spur formula 0:0:0. Hind coxal tubercle absent. Hind tibial macrochaetae absent. Postmetacoxal bridge absent.

Abdomen. Male terminalia with epandrium simple, not containing hypandrium ventrally. Epandrium wider than long; strongly notched anteriorly. Tergite 10 absent. Hypoproct triangular (rounded posteriorly); flattened, distinct from sclerites above cerci; with or without setae. Cercus displaced away from epandrium; widely displaced from one another, separation distance greater than three quarters width of cercus; held vertical in relation to rest of abdomen; in posterior view flat. Hypandrium fused entirely to gonocoxites; in L. alaskensis , with broad ventral processes separated by a central notch. Gonocoxite smooth dorsally, without sinuous ridge leading to gonocoxal apodeme. Gonocoxal apodemes absent. Sperm sac not developed into bulbous sac or separate lobes. Lateral ejaculatory processes absent. Ejaculatory apodeme reduced, nearly absent. Ejaculatory apodeme laterally compressed. Aedeagal tines absent. Endoaedeagal process absent. Female unavailable and remains undescribed.

Larva. Unknown.

Biology. Litoleptis is unusual in having a pan-Pacific distribution, with species endemic to Alaska, the Philippines, China, and Chile ( Chillcott 1963; Hennig 1972; Yang et al. 1997).

Literature. Chillcott (1963) illustrated the head, wing, and male genitalia of L. alaskensis . Hennig (1972) compared the three species currently described in the genus, and illustrated the head, wing and male genitalia of L. chilensis .

Notes. The holotype and paratype of Litoleptis alaskensis were collected at Cape Thompson, Alaska, 26– 29 July 1961, by B.S. Heming. There are two Cape Thompsons in Alaska. The one where L. alaskensis was collected is (most likely) near the Project Chariot bioenvironmental study, which was active in the late 1950s to early 1960s. It is located on the Chukchi Sea coast, 26 mi SE of Point Hope, Arctic Slope; 68.14°N, 165.98°W.