72 Bulletin of the Brooklyn Entomological Society Vol. XVI 



tion of the spiracle of the third abdominal sternite (being located 

 in the middle of the membranous parts on the sides of the 

 sternites, whereas in the other groups it is placed in or near the 

 anterior corners), all serve to very definitely separate this sub- 

 family from the others. In addition, it contains all of the aphi- 

 dophagous forms, except those of Pipi^a, a biological character 

 of considerable importance. The hitherto aberrant-considered 

 genus, Chrysotoxuni, undoubtedly belongs here. 



The above characters seem to indicate that the Syrphidae have 

 split into two main groups : the Syrphinae, and all of the other 

 groups considered collectively ; and that the Syrphinae are special- 

 izing in structure from the cephalic aspect and the remainder of 

 the family from the caudal aspect. Nausigasterinae are an ex- 

 ception to both of these groups, as they appear to be specializing 

 from both aspects. 



The genera- of the Syrphinae have not yet been defined satis- 

 factorily. Many of them have been based on weak characters 

 and frequently there are neither distinct nor, sometimes, natural 

 divisions. The Melanostomini are not sharply defined from the 

 Syrphini ; several species in Syrphus are doubtfully retained 

 there. The generic limits in the Melanostomini are very weak, 

 being based mostly on male characters. Rhysops and Xanthan- 

 drus are not separated in the table from Melanostonia. 



A number of the present genera of Syrphini are in reality 

 merely aberrant species of the genus Syrphus; and in the case of 

 Didea, D. laxa should, according to the present concepts, be placed 

 in a genus of its own, or more preferably be considered congeneric 

 with Syrphus; it shows more relationship with species of Syrphus 

 than with D . fuscipes. 



Likewise the genus Xanthogrmmna is a heterogenous one ; X. 

 flavipes is a typical Xanthogramma. The remaining species have 

 very little of the habitus of flavipes and evidently are more or less 

 unrelated species of Syrphus with yellow lateral mesonotum mar- 

 gins. The European genus Doros is here included for Xantho- 

 gramma aequalis Lw. 



Ocyptamus (Baccha) jactator Lw. clearly connects the Bac- 

 chini with Syrphus. 



{Continued in December number) 



