612 DIPTERA. 



bearing a little bristle. Their larvse, or young, are fleshy, 

 whitish maggots, which never cast their skins, but, when 

 the pupa state comes on, shorten, take the oblong-oval 

 form of an egg, and become brown, dry, and hard on the 

 outside. This immense tribe includes the various kinds of 

 flesh-flies, blow-flies, house-flies, dung-flies, flower-flies, fruit- 

 flies, two-winged gall-flies, cheese-flies, and many others, 

 for which we have no common names, but all composing 

 the tribe of Muscans, or Muscad^. Some of these flies 

 do not strictly conform to the foregoing characters of the 

 tribe, in all respects ; but the exceptions are few in number, 

 and the most remarkable of them wifl be noticed in the 

 following pages. 



i\Iany flies of this tribe are parasitic in their larva state, 

 then- young living and undergoing their transformations 

 within the bodies of other insects, particularly in caterpillars, 

 which they thereby destroy. These flies belong chiefly to 

 the family of Tachinad^, a name applied to them on account 

 of the swiftness of their flight. In form they somewhat 

 resemble house-flies ; like them, they have very large wing- 

 lets, and their wings spread apart when they are at rest. 

 Thev are easily distinguished, however, by the stiff" hairs 

 wherewith they are more or less covered, and by the bristles 

 on their antennae, which are not usually feathered. A large 

 fly of this kind, the Tachina vivida (Plate VIII. Fig. 1) of 

 my Catalogue, is often seen on fences, and on plants, and 

 sometimes in houses, towards the end of June and during 

 the month of July. Its large, oval hind body is of a clear 

 and lio-ht red color, with two or three black spots, in a 

 row, on the top of it, and a thick row of black bi'istles across 

 each ring. The face is grayish white, like satin, and the 

 eyes are copper-colored. The thorax is gray, with brownish 

 lines upon it. The antennse, proboscis, and legs are light 

 red. Its body is short and thick, and is about half an inch 

 lona\ and its wings expand rather more than nine tenths 

 of an inch. 



