THE PARASITE OF THE TIGER CATERPILLAR. 



During the spring months the brown cocoons of the tiger 

 caterpillar may be found under boards, logs, fence-rails, and 

 similar shelter beside fields and highways. It will be worth 

 your while to collect a dozen or more of them and keep them 

 indoors in a glass-covered box. 



During the next two or three weeks the brown moths are 

 likely to emerge from the cocoons, but from a few of the 



cocoons there are likely to come 

 forth one or more entirely differ- 

 ent creatures. These are slender 

 bodied insects, having four trans- 

 parent wings. They resemble 

 bees or wasps in their general 

 appearance. 



These peculiar insects are ich- 

 neumon flies. The way they came 

 to be in the cocoon of the tiger 

 caterpillar may be explained thus : 

 Many weeks before, a four-winged fly laid one or more eggs in 

 the body of the tiger caterpillar. The egg- soon hatched into a 

 tiny whitish maggot which absorbed 

 the blood and other liquids in the 

 body of the caterpillar. It contin- 

 ued to grow for some time, and at 

 last, after the caterpillar had spun 

 its cocoon, the maggot killed the 



caterpillar and changed to a pupa inside the cocoon. There it 

 remained until the time for another change. Then it became 

 a full-grown ichneumon fly and gnawed a hole in the cocoon. 



20 



Fig. 21. — Ichneumon Fly. 



Fig. 22. — Larva of Ichneumon Fly. 



