1 86 PRINCIPLES OF FARM PRACTICE 



It is important to know the life history of our common 

 insects and also when and where to look for each stage, be- 

 cause such knowledge is needed for insect control. If the 

 various stages in the life history of an insect are recognized, 

 some one stage is likely to be found weaker or more easily 

 reached than others. This should indicate what to do in 

 order to prevent or reduce the injuries caused by this insect. 

 For example, the codling moth lays its eggs on the small 

 apples about the time the blossoms fall in the spring. Soon 

 the egg hatches, and the larva, a little worm, eats its 

 way into the young apple. Later, after the worm and the 

 apple have increased in size, the apple falls to the ground. 

 Then the worm crawls out of the apple and finally goes up 

 the trunk of the tree to hide beneath some scale of bark. 

 Here it changes into the pupa and later into a moth, ready 

 to start a second generation. There are two points in this 

 life history that suggest a means of control. First, the hatch- 

 ing period; if a poisonous spray is applied at this time the 

 young larva is very likely to be poisoned as it eats its way 

 into the young apple; second, the pupa-forming period, in 

 mid-summer. At this time the worms crawl up the lower 

 part of the tree trunk to find a shelter beneath the bark 

 scales. If these scales are scraped off and a band of burlap 

 is tied about the tree trunk two or three feet from the ground, 

 the worms hunting for shelter will crawl beneath the burlap 

 band. After they have collected under the band and formed 

 pupae, it may be removed and the pupae destroyed. 



How insects secure food. It is important to know whether 

 a particular kind of insect gets its food by biting or by suck- 

 ing. If it gets its food by biting, the application of some 

 poison in form of a spray will be effective for control; 

 naturally the insect will eat some of the poison when eating 



