118 ENTOMOLOGICAL SOCIETY 



genus Lomatia (Stygia) iruthe Bombyliidtz, and which is now 

 known as Agnotomyia elongata Say. This species was for a 

 long time an enigma to dipterologists. The genus is closely 

 related to Triptotricha, from which it is described as differing 

 in having only one spur on the front tibiae, only four posterior 

 cells in the wings, and the last posterior vein arising from the 

 discal cell. In the above paper Dr. Williston calls attention 

 to the fact observed by Lcew that specimens of T. fasciventris 

 often occur in which there is an abbreviation of the third pos 

 terior vein, and adds that he has observed also that rarely the 

 last posterior vein arises from near the base of the discal cell. 

 Supposing the bare possibility of a Triptotricha with the neu- 

 ration of Agnotomyia, he notes that the two spurs on the front 

 tibiae would serve to distinguish the former, and says that in 

 the three species of Triptotricha known to him all the tibiae 

 have two spurs. It will be seen that Dr. Williston had not at 

 that time critically examined T. rufithorax Say, which has 

 only one spur on the front tibiae. I have found that in this 

 species also the third posterior vein is often abbreviated, while 

 in two instances I have seen the last posterior vein arising 

 from the discal cell, being well removed from the second basal. 

 It is frequently the case that this vein (last posterior) is con 

 tinuous with the cross- vein that separates the discal and sec 

 ond basal cells. Twenty-four specimens of rufithorax that I 

 have examined possess at least an abbreviation of the third 

 posterior vein. One of this species collected near Rock 

 Creek, D. C., June 15, is peculiar for possessing an extra 

 cross-vein in the left wing, which cuts off the outer one- 

 eighth of the first basal cell, and is parallel with the small 

 cross-vein of the wing. 



The three species of Triptotricha above referred to by Dr. 

 Williston as having two spurs on all the tibiae I infer to be 

 fasciventris, discolor and lauta all Lcew's species. I have 

 seen the last species, and it possesses two front tibial spurs. 

 L,oew, in his description of lauta, either overlooked the two 

 spurs or, what is more likely, believed Say's rufithorax to also 

 possess two, for he mentions the points of difference between 

 the two without noticing this distinction. The genus Tripto 

 tricha must be accepted, in the strict sense, as including the 

 three forms which L,cew described, for which he erected his 

 genus, and all of which possess two front tibial spurs. Say's 

 species falls in another natural division as it has only one front 

 tibial spur. I have seen also a single 9 of an undescribed 

 species from the Pacific coast which has only one front tibial 

 spur, and differs from rufithorax chiefly in its larger head. 

 These constitute a separate group, but as there are yet only a 

 few species to be located here, and as these two groups do not 



