1909] Robberflies of the Genus Asiliis 137 



description of such species as have been brought to their atten- 

 tion for names. There is in the collections of the country, there- 

 fore, a quantity of undetermined material and not a few undes- 

 cribed species which are a hindrance to investigators as well as 

 to the painstaking amateurs whose ideals are to have all speci- 

 mens named and grouped in reference to some particular system" 

 under a series of neatly written labels. 



The genus here considered is classified in the Asilinae, one of 

 the four subfamilies into which the family is divided in North 

 America. In the Asilinae the species are of medium to large 

 size, long and slender form and black, yellowish, brownish or 

 gray color, with a close general resemblance throughout the 

 group. The antennae each are composed of three segments of 

 which the first is longer than the second, and the third longest 

 of all ; the latter segment at its apex bears a long style or arista 

 composed of two segments of which the first is very short. In 

 the wing the marginal cell is always closed, as are the fourth pos- 

 terior and anal cells, and there are either two or three submarginal 

 cells of different lengths. The members of the genus Asilus are 

 typical of the subfamily, the antennal arista is naked, the poster- 

 ior branch of the third vein reaches the margin of the wing be- 

 yond its apex, there are two submarginal cells in all cases and the 

 veins which close the discal and first posterior cells are not 

 parallel. 



Ever since Loew monographed the European robberflies in 

 1848 and divided the genus Asilus of Linnaeus into groups with 

 separate names, students have been at variance as to whether or 

 not Loew's names should be considered as genera. In Diptern- 

 fauna Sudafrica's issued in i860, Loew himself raised his names 

 to generic rank, but Schiner, one of the foremost students of Dip- 

 tera, writing at about the same date considered Asilus in the wide 

 sense. Later European students in the main have been inclined 

 to follow Loew as have some Americans. Lately, however, there 

 is a tendency to drop Loew's names and include all of the species 

 concerned in the genus Asilus, thus following Schiner' s arrange- 

 ment. Thus Pandelle, an European, writing as late as 1905, 

 and Williston of this country, in his revised edition of North 

 American Diptera, published in 1908, have made it plain that 

 they prefer the latter. Personal inquiry brings out the fact 

 that nearly all of the prominent dipterologists of the United 

 States are ready to accept Williston's views in the matter. 



