Diptera 297 



bristly above; usually light colored flies. 

 Hippelates, Oscinus, and other genera. (See 



also mmm OsciNrD.ffi; 



mm. Cell M and cell first M2 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.ffi; 

 mmm. The Geomyzid^, Agromy7id^, Psilid^, 



TrYPETID/E, RHOPALOMERID.E, BORBORID.E 



and DiOPSlD^ differ in various particulars 



from either the OsciNID.ffi; and the SEPSID.ffi 



noted above. 



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



frequently projecting from below the upper one; both 



posthumeral and intraalar macrochaetas 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- 



chaetse 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.ffi;. 



1. The costal vein ends at the tip of R4+6, Mi+2 

 straight, not reaching the wing margin, hence 

 cell R5 wide open (fig. 163J); 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- 

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

 favor in Europe, Townsend, in J908, 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 .\Torth American Diptera, though w e 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. 



