Isoneuromyia nigribasis Evenhuis, n. sp.

(Figs. 15, 22, 33, 38)

Diagnosis

Similar to splendida in both having the basal antennal flagellomeres brown and the apical ones yellow to orange. It can be easily distinguished from splendida by the distinct and separate mesonotal stripes (coalesced in splendida) and the normally shaped lower tooth at the apex of the gonostylus (this tooth shaped like a shark’s tooth in splendida).

Description

MALE. Lengths: Body: 12.2 mm; wing; 8.3 mm.

Head. Vertex and occiput immediately behind ocelli black; remainder of occiput orange with fairly dense small black recumbent hairs. Ocelli in horizontal line. Frons dark brown, bare. Antennae: scape and pedicel cup­shaped, brown. Flagellum: segments slightly compressed; flagellomeres 1–6 brown; flagellomere 7 reddish brown; flagellomeres 8–14 yellowish. Face brown, silvery pruinose with small black hairs apicolaterally. Palpi reddish brown. Proboscis dark brown.

Thorax. Mesonotum brownish yellow with three black stripes (Fig. 15), medial stripe extending anteriorly to pronotum. Scutellum dark brown. Mesonotum with uniformly distributed small recumbent black hairs dorsally, patch of thick black setae above wing root and on posterior margin of scutellum. Prescutellar area tapering to scutellum. Pronotal lobes dark brown with dense black setae. Pleura and mediotergite dark brown, bare. Halter orange.

Legs. Coxae reddish brown with black hairs; fore and hind coxa with spot of black basally. Fore and mid femora reddish brown, hind femur black, all with recumbent black hairs. Fore tibia with small black tibial pecten apically. Tibial spurs black. Fore basitarsus 1.3 x length of fore tibia. Mid and hind basitarsi subequal in length to lengths of respective tibiae. Claws minute.

Wing (Fig. 22). Grayish yellow hyaline anteriorly along costal margin, becoming more clear posteriorly; with brown infuscation apically from costa to apex of cell m2; apex of cell cua1 with small cloud of brown apically; vein R4 slightly sinuous, ending in C slightly beyond end of R1.

Abdomen. Tergites I–III black with yellow basally, dense black recumbent hairs on black portion of segments, bare on yellow portion; tergite IV reddish yellow with pair of sublateral brown longitudinal stripes; tergites V–VII predominantly yellowish orange with scattered black tomentum laterally, dense dorsally; tergite VIII yellow with yellow hairs. Sternum patterned as on tergites except I–III with brown color medially.

Hypopygium. Not dissected. Gonocoxites grayish brown. Gonostyli yellowish brown, densely fine yellow pilose, apex with two dark black dentae.

FEMALE. Unknown.

Types

Holotype ♂ (BPBM 16,595) from: LAOS: Vientiane Province: Ban Van Eue, 30 Mar 1966, native collector. [The actual locality is Ban Van Heue, 20 km E of Phou­kow­kuei in Vientiane Province, Laos. However, all the labels have the locality spelled as “Ban Van E ue”, which is kept here in order to allow retrieval of the specimens by future workers.]

Etymology

The species epithet derives from the Latin niger = black + basis = base, referring to the dark basal flagellomeres of the antennae.