270 



FUNDAMENTALS OF AGRICULTURE. 



PLANT LICE, SHOWING HOLES CLT IN THEIR 



THEM. 



(Photograph by M. V. Slingerland.) 



white objects which many people think are the eggs of 

 the caterpillars themselves. Really, these are the co- 

 coons of a parasitic insect, the larvae of which have 



actually lived within 

 the body of the cat- 

 erpillar and weak- 

 ened it so that it 

 finally dies. It is 

 easy to see how 

 such parasites help 

 the grape and to- 

 mato grower. 



Again, where 

 green plant lice be- 

 come abundant on 

 cabbage or on grain 



BACKS BY PARASITES THAT HAVE KILLED they may be found 



sooner or later, a 

 large part of them 

 dead with their bodies greatly swollen and with a cir- 

 cular hole cut in their backs. These lice have been 

 killed by a tiny wasp-like insect that laid its eggs within 

 the body of the plant louse. When the egg hatched, 

 the small larva lived within the body of its host, and 

 finally when the parasite became full grown it cut a 

 hole in the back of the louse, and came out ready to 

 attack other lice. The so-called green-bug that injures 

 the wheat in Texas in some years is subject to tremen- 

 dous attacks by just such a parasite. In fact, during 

 seasons when the green-bug is not numerous enough to 

 cause trouble it is certain that these little bugs have 

 been at work killing it. 



These are only a few instances of the manner in 

 which the farmer is helped by his friends, the insect 

 parasites. If it were not for these various kinds of 

 parasites working all the time, and in places that we 

 know nothing about, our farm and garden crops and 

 fruits would be destroyed much more than they are. 

 EXERCISE. Look on peach and plum trees and various weeds, 



