'ISO XEBRASKA STATE HORTICULTURAL SOCIETY 



pletion of this stage it "hatches" into a fully matured insect, eats a small 

 round hole in the shell of the egg and starts en a search for more eggs 

 to be victimized by the next generation. While the eggs have their para- 

 sites largely cofined to the one group of family of insects, the larvae 

 are not as fortunate, for their enemes are much more numerous and 

 differ greatly in habits and general appearance. Two large divisions 

 are represented: The two-winged insects or Diptera which are properly 

 called flies, and four-winged insects or llyraenoptera, some of whicli 

 might commonly be mistaken for small dark colored bees while others 

 superficially resemble the long bodied wasps. 



The parasitic flies are divided into four groups which may be recog- 

 nized without much difficulty. Tbe large group is composed of flies 

 called Tachinidae and are the hardest to distinguish from their close 

 relatives such as the house-fly, blow-flies, and flesh-flies. These charac- 

 ters, however, are sufflcient to identify the group, namely: The presence 

 of few or many spines scattered over the body, and the bristles on the 

 antennae or "feelers" which are bare instead of feather-like. A second 

 group, Dexiidae, closely resembles the Tachinidae and these flies may be 

 distinguished by usually having longer and more slender legs and the 

 bristles of the antennae being feather-like. The members of these groups 

 which are destructive to moths and butterflies choose the larvae as 

 hosts, never attacking the eggs or adults and seldom, if over, the pupae. 

 The egg is deposited on the skin or hair of the caterpillar to which it is 

 fastened by a viscous fluid. When it hatches the little worm bores its 

 way beneath the skin of the host. If the young parasite were to feed 

 upon the vital parts of the caterpillar, the host would soon die and the 

 body completely dry up long before the parasite reached maturity, but 

 there is a wisdom which prompts the parasite to feed only on the fatty 

 tussues of the body. This does not seem to greatly discommode the 

 caterpillar which continues to eat and produce tissue for the little guest. 

 It is only when the parasite becomes almost full grown that the cater- 

 pillar ceases to eat and begins to sicken and die. The larva of the 

 parasite may leave the caterpillar and burrow in the ground or crawl to 

 some protected place and there pupate, or it may pupate within the body 

 of the host. In either case the caterpillar never recovers. There are 

 »ome interesting observations with reference to this method of para- 

 sitism a few of which are worth mentioning at this time. Since all 

 caterpillars shed skin several times before reaching maturity the effec- 

 tiveness of Dipterous parasites is greatly lessened. The eggs may be 

 attached to the back of a caterpillar shortly before a molt takes place, 

 and the caterpillar may crawl away leaving the eggs attached to the 

 empty skin; rejoicing, shall we say, at the narrow escape. In spite of 

 this difficulty the army-worm plague which so often breaks out in various 

 localities is usually, to a large extent if net completely, controlled by 

 Tachinid parasites. A badly infested field will be simply swarming with 

 these flies and owing to their numbers and their persitence in depositing 

 eggs sause such mortality that few army-worms survive for the next 



