Teucholabis (Teucholabis) tenella Alexander 1970

Teucholabis (Teucholabis) tenella

Size small (wing of male to about 6.5 mm); mesonotal praescutum light chestnut brown, humeral and lateral borders light yellow, pleura light yellow with a narrow dark brown longitudinal stripe; halteres with knob light yellow; fore and middle legs with femora, tibiae, and basitarsi yellow, tips narrowly dark brown, remainder of tarsi dark brown, posterior legs with femora and tibiae almost uniformly yellow; wings pale yellow, unpattemed except for the small pale brown stigma and a darkening over the cord, Sc1 ending beyond midlength of Rs; abdominal tergites conspicuously patterned with yellow and brownish black, in male with broad blackened areas on either side, median and posterior regions yellow; male hypopygium with spine of basistyle pale, dilated at midlength, thence narrowed into a spine; mesal flange with margin smooth; terminal spine of aedeagus slender, curved.

MALE.—Length about 6.5–7 mm; wing 5.5–6.5 mm; antenna about 1.4–1.5 mm.

FEMALE.—Length about 5–6 mm; wing 4.8–5.5 mm.

Rostrum relatively short, chestnut brown, palpi brownish black. Antennae black; flagellar segments oval, shorter than their verticils. Head yellow.

Pronotum and pretergites light yellow. Mesonotal praescutum with 3 virtually confluent light chestnut brown stripes, central area paler, humeral and lateral borders light yellow; scutal lobes light brown, midregion and posterior calli yellowed; scutellum clear light yellow, parascutella darker; mediotergite light brown, cephalic border darker, lateral margins yellowed, pleurotergite light brown, posterior border paler. Pleura light yellow, with a narrow dark brown longitudinal stripe extending from the cervical region to the pleurotergite. Halteres with stem obscure yellow, knob clear light yellow. Legs with all coxae and trochanters light yellow; fore and middle legs with femora, tibiae, and basitarsi yellow, tips narrowly dark brown, remainder of tarsi more uniformly dark brown; posterior legs almost entirely yellow, tips of femora and tibiae not or scarcely darker, outer segments infuscated; 5th tarsal segment with a strong basal epicondyle; no modification of basistyle. Wings (Figure 44) pale yellow, stigma brown, subcircular; cord narrowly darkened, the color virtually restricted to the veins, remaining veins yellow, m a little darker. Costal fringe of proximal third of wing relatively long and conspicuous. Venation: Sc long, Sc1 about opposite two-thirds the length of Rs; R2+3+4 from about one-half to two-thirds R2, cell R2 at margin more extensive than cell R4; m-cu close to fork of M.

Abdominal tergites conspicuously patterned with yellow and brownish black, in male the 2nd segment darkened medially, succeeding segments with broad black areas on basal two-thirds, the median region and posterior borders yellow, in cases the base of segment uniformly darkened, the median yellow pattern poorly indicated or lacking; hypopygium yellow; sternites more uniformly yellow; segments with long erect pale setae. In female abdominal tergites more uniformly dark brown, posterior borders obscure yellow, more extensive on anterior segments. Male with sternal pocket of 5th segment small and simple, including about 10 marginal setae that are directed inwardly, the laterals stouter, with about 4 smaller setae and longitudinal rows of microscopic setulae in the discal area; no definite setal pocket on 6th sternite. Male hypopygium (Figure 50) with spine of basistyle, b, a flattened pale blade, its outer end narrowed into a spine; mesal flange of style relatively small, the darkened margin entire, with a few small setae near posterior end. Outer dististyle, d, a long slender blade bearing a small weak marginal spine beyond midlength; inner style with base a flat darkened blade, the free outer end shallowly bidentate, the teeth widely separated. Aedeagus with terminal spine slender, curved, basal enlargement with 5 setae, the outer unpaired bristle long.

Holotype, male, Clarke Hall, Dominica, 11–20 January 1965, in Malaise trap (Wirth). Allotopotype, female, 1–10 February 1965 (Wirth). Paratopotypes, both sexes, 11–20 January, 1–28 February, 1–10 March 1965, chiefly in light traps (Wirth); 13 June 1966 (Steyskal), 10 October 1966 (Gurney). Paratypes, both sexes, Cabrit Swamp, 23 February 1965, light trap (Wirth); Manets Gutter, 10 March 1965, light trap (Wirth); 804.7 m (0.5 mile) east of Pont Casse, 27 January 1965 (Wirth), 3,218 m to 4,828 m (2 to 3 miles) east of Pont Casse, 13–21 October 1966 (Gurney); Portsmouth, 2 March 1964 (Bray); Syndicate Estate, 5 March 1964 (Bray).

Teucholabis (Teucholabis) tenella has somewhat the appearance of T. (T.) complexa Osten Sacken, T. (T.) jocosa Alexander, and similar species, differing especially in the pattern of the legs and in hypopygial structure, including the aedeagus and lobes of the basistyle. This may be the species recorded from Saint Vincent by Williston as T. (T.) complexa but is an entirely distinct fly from the true T. (T.) complexa of eastern North America.

Rhabdomastix Skuse, 1890, pp. 828–829—Alexander, 1947b, pp. 318–322.