32 R. W. CROSSKEY 



more or less white. Facial pollinosity white or very pale yellowish. Smaller 

 species, length not exceeding 13 mm ........ 20 



20 Proclinate orbital pair of setae very strong, longer and stronger than the strongest 



frontal setae. $ third antennal segment enlarged and widest near the middle [? 

 angusticauda]. $ postabdomen elongate-subcylindrical with small terminal 

 claspers, the tubiform T6 + 7 subequal in length to the remainder (Text-fig. 130) 

 [? costalis}. Tibiae with the paler parts reddish to dark reddish brown and not 

 much contrasting with the blackish bases. Wings rather evenly and faintly smoky 

 brownish, the dark colour only intensified on the costal margin or weakly and 

 indefinitely towards the tips . . . . . . . . .21 



- Proclinate orbital pair of setae weak, subequal in size to or smaller than the strongest 



frontal setae. Third antennal segment not noticeably sexually dimorphic, long 

 and narrow in $ as in $, parallel-sided or slightly widening so as to be broadest at 

 the apex when seen in profile. $ postabdomen not unusually elongate, T6 + 7 

 much shorter than the terminal part and not tubiform, the terminal claspers 

 moderately large. Tibiae with the pale parts yellowish and strongly contrasting 

 with the dark bases. Wings usually strongly darkened brown antero-apically, 

 the apical intensification of the brown colouring conspicuous to naked eye 

 (occasional specimen with wings only faintly smoky throughout) ... 22 



21 Palpi yellow. Bend of vein M approximately equidistant between m-cu and the 



wing margin, changing direction at only slightly more than a right-angle; cell R b 

 short-petiolate [? variable]. Ocellar setae very weak, obviously smaller than 

 frontal setae. Parafrontals with a sharply demarcated silver pollinose spot 

 between the insertions of the prevertical and proclinate orbital setae and bare and 

 shining above the prevertical seta insertion. Abdominal dorsum with pale 

 pollinosity on about the basal third of T3 and basal half of T4 angusticauda Townsend 

 [See annotation following second half of this couplet.] 



- Palpi brown with the apices paler tawny. Bend of vein M much closer to m-cu than 



to the wing margin (unusually remote from latter), changing direction at a very 

 widely obtuse angle; cell R b open [? variable]. Ocellar setae long and fine, sub- 

 equal in size to frontal setae. Parafrontals with silvery pollinosity between 

 insertions of prevertical and proclinate orbital setae and also above insertion of 

 the former (at least along eye-margin) (the pollinosity appearing not to form such 

 a discrete spot as in angusticauda but only holotype known which has head slightly 

 greased). Abdominal dorsum with exceptionally narrow bands of pale pollinosity, 

 that on T3 occupying about basal one-fifth and that on T4 about basal one-sixth 

 of tergite length ........ costalis Townsend 



[It is possible that costalis (known only from $ holotype) and angusticauda 

 (known only from $ holotype and one other $) are opposite sexes of the same 

 species but evidence is insufficient to justify synonym}'.] 



22 Basicosta uniformly yellow or yellow-orange, contrasting in colour with the dark 



tegula. Wings usually appearing faintly yellowish on most of basal half and 

 this weak yellowed appearance slightly contrasting with the darkened smoky 

 brown apex, the basal parts of the long veins yellow and obviously paler than the 

 darker brown apical parts. 9 palpi slender (only with the usual inconspicuous 

 swelling at the extreme tips). $ postabdomen with the sides of sternite 6+7 

 produced into swollen lobes bearing many irregular stubby spines (Text-fig. 134), 

 and without spines (hairs only) on the posteroventral corners of T6 + 7. [<J 

 postabdomen as Text-fig. 125] ...... imbuta Wiedemann 



- Basicosta yellowish brown to dark tawny brown, colour more intense on anterior edge 



not noticeably contrasting with the dark tegula. Wings not appearing at all 

 yellowish basally but with some faint tawny brownish infuscation that is paler 

 than the brownish colouring towards the apices, the long veins only slightly and 

 inconspicuously paler proximally than distally. °- palpi strongly clubbed. $ 



