PARASITIC INSECTS. 



15 



burrow through the earth and devour the insects 

 found therein. 



Parasitic insects differ from their predaceous 

 cousins, in that they develop within the bodies of 

 their victims and- thus destroy them. These, also, 

 are exceedingly numerous, both in individuals and 

 species. A good illustration of the habits of this 

 class is found in the small, four-winged, black fly 

 (shown natural size and magnified at the right in 

 Fig. 5), that destroys the common Grape Caterpillar, 

 an insect closely related to the familiar Tomato Worm 

 or Tobacco Worm. This fly deposits a number of eggs 

 beneath the skin of the caterpillar, and these eggs 

 soon hatch into minute worms or maggots that ab- 

 sorb the body juices of the worm and develop at his 

 expense. After a few weeks these maggots become 

 full grown, and burrow their way out through 

 the skin of their hap- 

 less and helpless 

 host. They then 

 spin their whit e, 

 silken cocoons (Fig. 

 5 ) upon his back. 

 Within these cocoons 

 they change to the pupa or chrysalis state. About 

 two weeks later they again change, and the legless, 

 little maggots find themselves transformed into neat 

 and pretty black flies, with four wings and six legs, 

 like the one which a few weeks before deposited in 

 the caterpillar the eggs from which they developed. 



1g. 5. Caterpillar with C 

 Adult Parasite at right. 



cons df Farasit: 

 Latter magnified. 



