148 ERNEST A. BACK. 



very dense and sometimes in tufts as in some Cyrtopogon 

 species; the bristles when present are usually confined to a 

 small area on the sides of the first, or first and second seg- 

 ments, though sometimes present on the posterior margin of 

 the first segment, but in the Laphystia and PsUocutms bristles 

 may be found on the sides of the following segments as well, 

 although such bristles are usually less prominent and shorter. 



Wings. — The wings are quite large, usually strong, and while 

 usually rather narrow are sometimes much broader, as in Hol- 

 cocephala species; in length they usually equal that of the abdo- 

 men, though in many species of Stenopogon are considerably 

 shorter. In color they vary from pure hyaline to deep black, 

 sometimes spotted, and again wholly or in part milky white. 



The Schiner system of vein and cell nomenclature has been 

 adopted. For the distribution of the veins and cells see PI. 

 II, Fig. 1, and compare with wings shown on the half-tone 

 plates following. Five posterior cells are usually present, but 

 in Townsendia, the anterior intercalary vein is lacking, thus 

 reducing the number to four. The marginal cell is always 

 open, but in Laphystia and Tricilis is so nearly closed that 

 question has arisen in the past whether these genera do not 

 more properly belong to the Laphrinae. Dr. Fr. Hermann,* 

 by a series of careful drawings, has shown that this cell is open 

 to considerable variation and has clearly demonstrated the 

 intermediate position of these genera between Dasypogoninse 

 and Laphrinae. This view has been held by Dr. Williston. 

 The submarginal cells are always open, as also are the pos- 

 terior cells with the exception of the first and fourth, which 

 may be open or closed; the anal cell may be either closed or 

 narrowly open. The closure of the first posterior, and often 

 the fourth also, is a matter of considerable variation, even 

 within the same species, or even the same specimen. The 

 fourth posterior seems more stable in this respect, but in such 

 a genus as Saropogon, is found to vary to a considerable ex- 

 tent. Sometimes the upper surface of the wings, especially 

 in Deromyia, bears areas of microscopic pubes which have 

 been used occasionally in the separation of species. The alula 

 is comparatively small. 



* Beitrag zur Keuntris der Asiliden, Ber. Ent. Zeit., Band L. '05; p. 31. 



