375 



flowers and never with prey, but my observations do not cover a long 

 enough period to permit a definite statement as to the habits of the 

 species of such genera as Holcocephala. The larger species, and par- 

 ticularly those that are of economic importance in the larval stages, 

 are predaceous almost exclusively, attacking bees, wasps, and even 

 other asilids, which they kill by inserting their proboscis through the 

 thin membrane of the anterior portion of the thorax just below the 

 dorsum, and through this opening extracting the body fluids. 



I have found no parasitic enemies of either larvae or pupae, but 

 the various stages of the species are preyed upon by insectivorous 

 birds and mammals, and even by members of their own family. 



Keys to Genera and Species 



larvae 



. 1. Maxillae with an angular incision on outer side about middle; ab- 

 dominal segments 1-6 each with circle of 6 pseudopods on the 



anterior half (Dasyllis (p. 380) . 



iCeraturgus^ (p. 379). 

 i Laphria. 



— Maxillae without an incision on outer side, posterior lateral extrem- 



ity more or less distinctly angulated 2 



2. Very small species, averaging less than 10 mm. in length; mandibles 



aborted ; penultimate abdominal segment as long as ultimate .... 

 Leptogaster flavipes (p. 377) . 



— Larger species, at least 15 mm. in length ; mandibles extending at 



least midway to apices of maxillae 3 



3. Maxillary palpi at least 3 times as long as their diameter (PI. LIV, 



Fig. 10) Asilus notatus (p. 385). 



— Maxillary palpi at most twice as long as their diameter 4 



4. Antennae indistinguishable ; short, robust species with distinct loco- 



motor elevations on venter ; maxillae without a distinct incision at 

 base of palpi Deromyia discolor (p. 384). 



— Antennae distinct; if the species is short and robust the maxillae 



have a distinct incision at base of palpi (PI. LIV, Fig. 5) 5 



5. Posterior discal cephalic hair much nearer to antenna than to pos- 



terior margin of head; body robust, slightly flattened dorso-ven- 



trally, the segments shorter than broad 



Promachus fitcliii (p. 383) . 



— Posterior discal cephalic hair nearly midway between antenna and 



posterior margin of head; body slender, rounded, segments longer 

 than broad Promachus vertebratus. 



PUPAE 



1. Head without sharp forward-directed thorns, at most with slight 

 carinated elevations ; abdomen with strong curved thorns and in- 

 tervening slender hairs Leptogaster flavipes (p. 377). 



