Diptera 
297 
bristly above; usually light colored flies. 
Hippelates, Oscinus, and other genera. (See 
also mmm . Oscinid® 
mm. Cell M and cell first M2 often separated by a 
crossvein; aijal 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® 
mmm. The Geomyzid®, Agromyzid®, Psilid®, 
Trypetid®, Rhopalomerid®, Borborid® 
and Diopsid® differ in various particulars 
from either the OSCINID® and the SEPSID® 
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® . 
1 . The costal vein ends at the tip of R-4+5, Mi+ 2 
straight, not reaching the wing margin, hence 
cell R5 wide open (fig. i63j); 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 Braaer and Bergen- 
stamm and of Girschner, with the modifications of Schnabl and Dziedzicki having obtained most 
favor in Europe. Townsend, in jqoS, 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. 
