360 NORTH AMERICAN DIPTERA. 



For further study of the family the reader is referred to 

 the various works of Brauer and Bergenstam, v. d. Wulp, 

 Townsend and Coquillett. 



The habits of the mature fly are similar for nearly all 

 the members of the group. They will be found on veg- 

 etation, on leaves or flowers, in such places as are fre- 

 quented by the hosts which they parasitize. Not a few 

 will be caught with the beating net. 



The larvae of the more typical Tachinidae are thicken- 

 ed, cylindrical and flattened below, the segments indis- 

 tinctly differentiated, with transverse and lateral swel- 

 lings, bare or provided with fine, short shines. They are 

 amphipneustic, the anterior spiracles small and point- 

 like or multipartite, the posterior stigmatic plates large, 

 strongly chitinized, and each with three, internally con- 

 vergent grooves. The antennae are wart-like, with two, 

 ocellus-like, chitinous rings, one lying below the other. 

 There are but two mouth-hooklets, porrect and but little 

 curved. The puparia are oval, with the segments slightly 

 differentiated; the skin is finely wrinkled, and both ends 

 are rounded. 



In Ocyptera and Gymnosoma, and probably in allied 

 forms, the larvae have a chitinous, anal stigmatic tube; 

 and the puparia have six or two, similar processes. The 

 larvae of Hyalomyia are translucent, smooth and meta- 

 pneustic, the mouth-hooklets very large; there are two, 

 short, divergent, anal tubes. 



The larvae of this group are all parasitic in habit so 

 far as known, and the parasitism is probably confined to 

 the early stages of other insects; and the individual fly 

 is not very particular in the choice of larvae which she 

 parasitizes. Their usefulness in keeping injurious in- 

 sects in check is immeasurable. 



By far the largest number of species are parasitic upon 

 L,epidoptera, of which not less than four hundred have 



