i go 



Nature-Study Agriculture 



How in- 

 crease is 

 checked 



Harmful 

 and 



beneficial 

 insects 



W. T. Shilling 



FIG. 142. Equipment for insect study : insects on cotton under glass; butter- 

 fly net ; block for mounting ; killing bottle (containing cyanide) ; insects 

 mounted on pins in glass-covered frame. 



eggs, which, within three weeks, pass through two inter- 

 vening stages and become mature flies ready to lay 

 more eggs. 



Insects are held in check through being destroyed by 

 each other and by diseases that kill great numbers of 

 them. If their increase were unhindered, they would 

 destroy all the food that is needed by man and animals. 



In their search for food insects may be either harmful 

 or beneficial to man. If there were no insects, some 

 crops would produce much larger harvests and some 

 could not be grown at all. The harm done by chinch 



