CHAPTER LXXVI 



INSECTS AND OTHER ORGANISMS 



448. Insects and useful plants. From the time when men 

 first began to cultivate plants for their own use, insects of one 

 kind or another have caused parts of each year's work to be 

 wasted. There are 

 early records of the 

 destruction caused 

 by locusts, and this 

 name has come to 

 be applied to many 

 varieties of insects 

 that move in hordes. 

 One of the plagues 

 of Egypt was a 

 swarm of locusts, 

 insects which are 

 referred to in the 

 Bible repeatedly. 



The first effort 

 in this country to 

 aid agriculture by 

 means of an official 

 investigation of in- 

 sect ravages was 

 made in the seven- 

 ties, when an outbreak of this pest did damage over an area 

 of about two million square miles west of the Mississippi River. 

 Since then the federal government and the various states have 

 kept up systematic work through experiment stations or special 



417 



FIG. 218. The potato beetle (Leptinotarsa 

 decemlineata) 



There are two or three broods a year. The full-grown 

 larva crawls into the ground, where pupation takes place. 

 The winter is passed underground in the adult stage. The 

 tachina fly, shown in the center, is one of the most impor- 

 tant enemies of the potato beetle. The fly lays eggs in the 

 larva of the beetle, and the maggots destroy their host 



