Diptera 297 



bristly above; usually light colored flies. 

 Hippelates, Oscinus, and other genera. (See 



also mmm Oscmnxffi 



mm. Cell M and cell first Mz often separated by a 



crossvein; anal cell present, complete, though 



frequently small; scutellum without spines 



or protuberances; oral vibrissae present; 



arista bare or short plumose; front bristly at 



vertex only; small dark flies. Piophila 



(fig. 99), Sepsis and other genera. . . SEPSID^I 



mmm. The GEOMYZID^E, AGROMYZID^E, PSILID.E, 



TRYPETID^;, RHOPALOMERIDTE, BORBORID^E 



and DiopsiDvE differ in various particulars 



from either the OSCINID^E and the SEPSID^E 



noted above. 



jj. Squamae well developed, usually large, the lower one 

 frequently projecting from below the upper one; both 

 posthumeral and intraalar macrochaetae present; 

 thorax with a % complete transverse suture; postalar 

 callus present and separated by a distinct suture from 

 the dorsum of the thorax; front of the female broad, 

 of the male frequently narrow, the eyes then nearly or 

 quite contiguous ; the connectiva adjoining the ventral 

 sclerites either visible or not; hypopleural macro- 

 chaetae present or absent; subcosta always distinct in 



its whole course, RI never short 



CALYPTRATE MUSCOIDEA* 



k. Oral opening small, mouth parts usually much reduced 

 or vestigial. This family is undoubtedly of poly- 

 phyletic origin but for convenience it is here con- 

 sidered as a single family OESTRID^E. 



1. The costal vein ends at the tip of R4+5, Mi+2 

 straight, not reaching the wing margin, hence 

 cell RS wide open (fig. 163}); squamae small; 

 arista bare; ovipositor of the female elongate. 

 Larvae in the alimentary canal of horses, etc. 



Gastrophilus 



m. Posterior crossvein (m-cu) wanting; wings 

 smoky or with clouds. Europe . . G. pecorum 

 mm. Posterior crossvein (m-cu) present, at least in 

 part. 



*The classification of the Muscoidea as set forth by Schiner and other earlier writers has 

 long been followed, although it is not satisfactory, being admittedly more or less artificial. With- 

 in the last two or three decades several schemes have been advanced, that of Brauer and Bergen- 

 stamm and of Girschner, with the modifications of Schnabl and Dziedzicki having obtained most 

 favor in Europe. Townsend, in 1.908, proposed a system which differs from Girschner's in some 

 respects, but unfortunately it has not yet been published in sufficient detail to permit us to adopt 

 it. From considerations of expediency we use here the arrangement given in Aldrich's Cata- 

 logue of North American Diptera, though we have drawn very freely upon Girschner's most excel- 

 lent paper for taxonomic characters to separate the various groups. 



It may sometimes be found that a species does not agree in all the characters with the synop- 

 sis; in this case it must be placed in the group with which it has the most characters in common. 



