616 ENERGOPODA 



wingmargin or slightly or even considerably {Leptogastei') open ; discal cell always 

 present, pentagonal, the long upper side being almost a straight continuation of the 

 base of the discal vein ; discal cross-vein placed not far from the middle of the 

 discal cell ; small cross-vein often present but sometimes absent through the upper 

 branch of the postical fork just touching the lower margin of the discal cell for a 

 short distance, though this character may vary in individuals of the same species ; 

 alulae usually distinct and well developed but very small or obsolete in many 

 Dasypogoninre and practically absent in Leptogaster (fig. 344) ; wing-membrane 

 ribbed or wrinkled. Squamae (alar) usually rather small but distinctly developed, 

 with usually a thick margin on which is a longer or shorter delicate or dense 

 fringe, and this fringe frequently becomes longer against the angle and may be even 

 tufted there {Stenopogon), in which case the tuft appears to act as a substitute for 

 the usual shelter hairs or bristly fan on the metapleurse ; when the wings are 

 closed the alar squamae when large may project upwards like lobes {Lai>]iria) ; 

 thoracal squamae absent or only present as a bare frenum. Halteres normal and not 

 at all concealed. 



This family is a very large one and contains some of the largest 

 known Dipteea, while none of the species are very small. Loew's words 

 in 1847 when he began his elaborate paper, "Ueber die europaischen 

 " Raiibfliegen (Diptera Asilica) " were as follows : " The family of the 

 " Eobber-flies is so sharply defined on all sides that at present no fly has 

 "been found concerning which it can be doubtful whether it is to be 

 " reckoned in this family or not. Nevertheless it contains a great wealth 

 " of most varying forms which renders their study especially attractive." 

 These words are almost as true now as when they were written, and 

 Loew then laid the strons; foundation for the elucidation of this immense 

 family which has well borne the enormous superstructure that has been 

 raised upon it, the Asilidm of the world being now probably better 

 worked out than any other family of Diptera, and this is all the 

 more remarkable when it is recognised that Loew made but little use 

 of the numerous chsetotactic characters. I do not know of any Diptera 

 (except the Apioccridce) having been placed in recent times in the Asilidce 

 which do not belong to them, nor have any true Asilidce been misplaced in 

 other families. As to the Apioceridce (which had been united by many 

 authors with the Mydaidce) Osten Sacken in his enthusiasm for 

 chsetotactic characters went too far, and began by sinking them as 

 only AsilincB in the neighborhood of Erax, Promachtis, etc., but sub- 

 sequently raised them to the rank of a subfamily of the Asilidce ; other 

 authors however have properly considered them to be a separate family 

 between the Mydaidce and Asilidce, being distinguished from the latter 

 by their venation, spatulate palpi, absence of face-beard, form of 

 antennae, etc. 



After excluding the Apioceridce the Asilidce form an extremely well 

 defined family. The Mydaidce are easily distinguished by their venation, 

 antennae, and absence of all bristles ; the Thcrevidce by their aerial habits 

 for which they have thin legs adapted for aHghting only, by their usually 

 furry pubescence, and by their short subcostal vein ; while the Umpidce 

 and Dolichopodidce (with which Osten Sacken associated them) are smaller 

 flies which have a much reduced venation. I am unable to accept Osten 



