INSECT PARASITES AND PREDATORS OF INSECT PESTS 21 



HYPERPARASITES 



The term " hyperparasite " is applied to that group of insects which 

 attack the true parasites themselves rather than the insect species 

 which cause injury to crops. They are thus injurious rather than 

 beneficial. As has already been stated, practically every injurious 

 insect has one or more primary parasites. Likewise these latter also 

 have their enemies which attack them. In nature this usually brings 

 about a balanced condition in which both the pest itself and the para- 

 sites which attack it are able to exist, but neither becomes over- 

 abundant. 



If a cluster of cocoons of Apanteles spun by larvae that have devel- 

 oped in the cabbage worm, the tobacco hornworm, the gypsy moth, or 

 any other of the numerous victims of this group of parasites, is set 

 aside for emergence it will often be found that a variety of minute 

 wasps rather than a single species will emerge from them. These are 

 the enemies of Apanteles, which have attacked the larvae in the co- 

 coons. From the puparia of the various fly parasites of caterpillars, 

 from those of hover flies, and from lacewing cocoons, wasps will often 

 emerge instead of the insects expected. There is thus revealed a 

 complicated relationship among the insects themselves which results 

 in a balance under natural conditions. This, however, is often upset 

 by the changes brought about by man. Instead of a varied vegeta- 

 tion, large tracts of land are brought into cultivation and devoted to 

 a single crop, frequently one which is new to the country. The result- 

 ing conditions have a marked effect upon the insect life of that section 

 and often result in disastrous outbreaks. 



