INSECTS 



in the next chapter, which treats of the cicada, a large 

 cousin of the aphids. 



When we observe, now, that different insects feed in 

 two quite different ways, some by means of the biting 

 type of mouth parts, and others by means of the sucking 

 type, it becomes evident that we must know which kind 

 of insect we are dealing with in the case of pests we may be 

 trying to control. A biting and chewing insect can be 

 killed by the mere expedient of putting poison on the out- 

 side of its food, if it does not become aware of the poison 

 and desist from eating it; but this method would not 

 work with the piercing and sucking insects, which extract 

 their food from beneath the surface of the plants on 

 which they feed. Sucking insects are, therefore, to be 



destroyed by means 

 of sprays or dusts 

 that will kill them by 

 contact with their 

 bodies. Aphids are 

 usually attacked with 

 irritant sprays, and in 

 general it is not a 

 difficult matter to rid 

 infested plants of 

 them, though in most 

 cases the spraying 

 must be repeated 

 through the season. 



When any species 

 of aphis becomes well 

 established on a plant, 

 the infested leaves 

 (Fig. 88) may be al- 

 most as crowded as an 

 East Side street on a 

 hot summer after- 

 noon. But there is 



Fig. 89. The way an aphis feeds on the 



juices of a plant 

 A, an aphis with its beak thrust into a rib of a 

 leaf. B, section through the midrib of a young 

 apple leaf, showing the mouth bristles from the 

 beak of an aphis penetrating between the cells 

 of the leaf tissue to the vascular bundles, 

 while the sheath of the beak is retracted by 

 folding back beneath the head 



■54 



