96 OUTLINES OF ENTOMOLOGY. 



it is impossible to remove them entire. The larvae, immediately upon 

 hatching, penetrate the skin of the insect and feed upon the non- vital 

 parts, so that, as a rule, the infested specimen is able to enter the 

 ground or to spin its cocoon before it is killed by the parasite. The 

 transformations of the latter then take place, and the flies appear very 

 shortly, or, in other cases, hibernate with the remains of their host and 

 emerge in the spring, at the season when fresh victims are most numer- 

 ous. Army worms and all cut-worms, various spinners and sphinxes, 

 grasshoppers, the larvae of the Colorado potato-beetles and many other 

 pests are destroyed by them. See Fig. 38. 



House-flies, blow-flies, etc. (Muscidce). No family of insects are 

 more familiar to us than the principal members of this group. At 

 almost any season of the year the student can obtain a fresh specimen 

 for examination, since many individuals of the common house-fly, and 

 also of the meat-fly, contrive to secure winter quarters in our warm 

 sitting-rooms and pantries. In these insects the greater portion of the 

 head is occupied by the eyes, which are, in some species, quite brightly 

 colored. The short antennae are plumy or sparingly bristled; the 

 labrum is elongated into a jointed proboscis, terminating in a pair of 

 broad, sucker-like flaps, which have their ridged inner surfaces closely 

 pressed together when not in use, but are spread out when lapping up 

 liquids, as may be easily observed in the House-fly. Other species have 

 the proboscis terminate in minute lancets. The body is sparingly 

 clothed with stiff hairs, and is either of a dull black and white or gray 

 , color, or, as in the " Blue-bottles " or green meat-flies, it is of a dark 

 metallic blue or green. The wings are transparent, the legs rather 

 stouter than in other flies and more or less hairy. The eggs are soft, 

 pearl-white and slender-oblong, deposited singly or in little bundles or 

 masses. The larvae are soft, white or whitish maggots, some of them 

 elongate- conical, thick and blunt at the hinder end and tapering to a 

 point in front ; others are slender and cylindrical ; most of them have 

 a smooth or somewhat ridged surface, but a few are hairy. Those of 

 the House-fly (Musca domestic^ Linn,) breed mainly in horse manure. 

 Another species which also breeds in stables and barn-yards is the 

 Lancet-fly (Stomoxys calcitraus, Linn.) It is scarcely to be distin- 

 guished from the common House-fly, except that when crawling or at 

 rest the wings are held more apart and the proboscis is more slender 

 and terminates in a point instead of a pair of fleshy lips. It bites 

 severely and is very troublesome to horses and cattle, nor does it hesi- 

 tate, upon occasion, to draw human blood. It is most abundant late 

 in summer and in early autumn. 



