148 ELEMENTARY LESSONS ON INSECTS 



infested with wireworms, by planting it to some other crop 

 that they will not eat, such as clover or alfalfa, the wire- 

 worms are starved out. It is fortunate for the farmer that 

 most of his crop pests will eat of but one or of a few closely 

 related plants. Proper rotation temporarily clears the fields 

 of some of them. He may clear the field of clover-seed 

 insects by mowing the hay early, before the larvae have 

 matured. He may further practice prevention by plowing 

 and planting at seasons unfavorable to his crop pests; avoid- 

 ing the cotton boll weevil, for example, by planting early; 

 the pea weevil and the Hessian fly by planting late. So, he 

 must know their times and seasons, their food and broods, 

 and their requirements as to temperature and shelter. 



7. Removal of breeding places. — Removal of the breeding 

 places is the most effective sort of prevention. It cuts off the 

 supply of pests at its source. It is practiced with house-flies 

 when the manure piles, that are their hatcheries, are drawn 

 to the fields and plowed under. It is practiced with mos- 

 quitoes when the temporary pools, in which their larvae 

 flourish, are drained. 



8. Destruction by other artificial means. — Hand picking 

 as for tomato worms; burning of infested stalks, as for the 

 European corn borer; plowing of the ground under plum 

 trees to break up the pupal cells of the plum curculio; oiling 

 of the rain water barrels to kill mosquito larvae: in these, 

 and in many other ways, countless insects may be destroyed. 



9. The use of natural enemies. — Chicken raising and small 

 fruit raising go well together because the chickens help to 



