INSECT PARASITES AND PREDATORS OF INSECT PESTS 



13 



a single caterpillar emerge from it on the same day. The cocoons 

 are spun upon the foliage nearby. The cocoon stage covers about 

 5 days, and the adult wasp then emerges by cutting away a circular 

 cap from one end. 



There are many other kinds of wasps that attack caterpillars. 

 These may attack the caterpillar directly during its feeding period or 

 they may attack the larva or pupa in the cocoon. Some of these 

 wasps are so small that several thousand may develop in each cater- 

 pillar, but as a rule only one matures. Often a collection of chrysa- 

 lids or cocoons will yield large numbers of these parasitic wasps and 

 flies instead of the butterflies and moths that were expected. 



Figure 8. — Cocoons of the wan 



Apanteles congregatus L. upon the tohacco hornworni. 

 Natural size. 



Among those parasites that develop in considerable numbers in one 

 host is a group which has the remarkable habit of producing many 

 individuals from one egg. A single egg is laid in the host egg, but 

 development is delayed until the latter hatches and the larva begins 

 to feed and grow; then the parasite egg grows and divides repeat- 

 edly, and finally may give rise to hundreds of individuals. Instances 

 are known of several thousand minute wasps developing in this way 

 in a single caterpillar. 



PARASITES OF WHITE GRUBS 



The white grubs found so commonly in the soil and which feed 

 upon the roots of grasses and cultivated crops are the larvae of 

 beetles known as " June bugs ", " May beetles ", etc. When these 



