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AJ^ ECONOMIC ENTOMOLOGY. 



ings, but in general type of structure. It is almost impossible 

 for any but the special student to distinguish between even the 

 sub-families, and yet these differ greatly in habit, some being 

 decidedly injurious and others as decidedly beneficial in the 

 larval stages. One of the peculiarities of all the members is very 

 short antennae, in which the terminal joint is long and stout and 

 furnished with a bristle or arista attached near the base. The 

 modifications of this bristle aid in distinguishing the groups. 



The Tachina flies, for instance, have the bristle entirely bare, 

 though otherwise many of them resemble the common ' ' flesh- 

 fly' ' or the ' ' blue-bottle. ' ' They are generally rather large, 

 robust in appearance, always bristly, and sometimes formidable 

 looking from the array of sharp spiny points projecting in every 

 direction. They are parasitic in habit, largely upon caterpillars, 

 and among them perhaps preferably upon cut-worms. Fre- 

 quently, where the latter are numerous, a large percentage will 

 be noticed with one or several little w^hite eggs attached on the 

 anterior segments, just back of the head, in such a position that the 

 larvae cannot possibly reach or destroy them. These eggs hatch 

 in a very short time into little maggot-like creatures that at once 

 bore through the skin of the caterpillar and live within its body, 

 feeding upon the fatty masses and muscular tissue not absolutely 

 necessary to life. When the maggots are full-grown and the 

 welfare of the caterpillar is no longer a matter of importance to 

 them, they feed on regardless of consequences, and the creature 

 dies. The maggots, sometimes without even attempting to get 

 out of their host, then change to barrel-shaped pupae. This is 

 accomplished by a contraction of the larval skin, which hardens 

 and becomes brown in color, releasing its hold at the same time 

 on the forming (true) pupa beneath. Occasionally the maggots 

 leave their host and make their way a little below ground to 

 pupate. Some of our large caterpillars attain their full growth 

 with as many as thirty or even more of these maggots feeding 

 upon their vitals. Some of the flies are very handsome and 

 strikingly colored, as, for instance, the Tachina vivida, in which 

 the abdomen is bright red, set with black spines, — a very remark- 

 able looking species. Others are black, the abdomen banded 

 with yellow ; but as a rule they are of a modest gray color, the 

 thorax rather obscurely streaked with blackish brown or gray. 



