220 THE INSECTS— ARTHROPODS 



An inch of rain water standing in a tin can may contain organic matter 

 that furnishes all the nourishment needed for dozens of mosquito wig- 

 glers to live and grow. Even solid dried wood, dry feathers, paper, and 

 starched clothing contain sufficient food for some insects to live on for 

 their entire life or a large part of it. There seems to be almost nothing 

 that has an organic origin that they have overlooked. 



Some insects are restricted in their feeding habits and can eat only 

 one or a small group of foods. Termites eat only wood ; silk worms stick 

 to mulberry leaves ; the cotton boll weevil restricts itself to the cotton 

 square or boll ; fleas must have the blood of a mammal ; certain wasp 

 larvae live only on spiders. Others are generalized and can have a varied 

 diet. The house fly is certainly not particular about what it eats ; it may 

 have the equivalent of soup from the body of a dead dog, an entree from 

 fried chicken on your dining table, and finish its meal with desert from 

 a pile of manure. The grasshoppers certainly do not restrict themselves 

 to grass as any farmer has learned from experience with the damage 

 which they may do to almost any kind of crop. 



The mouth parts of insects are highly specialized to accommodate the 

 kind of food eaten and the method of obtaining it. In general, there 

 are two types — biting and sucking mouth parts. Those with biting 

 mouth parts have hard chitinous jaws which work from side to side to 

 bite off and crush the food as it is taken into the mouth. In the other 

 group the mouth parts are fused to form a proboscis through which 

 liquid food may be drawn. This is often sharp on the end so that it may 

 be thrust through the skin of animals to suck blood, or through the epi- 

 dermis of leaves to suck the plant sap. In attempting to control insect 

 pests of plants it is important to know the kind of mouth parts which the 

 insects possess. A poisonous spray put on the leaves will kill those 

 with biting mouth parts, since they will eat the poison along with the 

 leaves. However, those with sucking mouth parts would not be affected, 

 since they stick their proboscis right through the poison and suck the 

 unpoisoned sap beneath. A contact spray that will reach the bodies of 

 these insects then becomes necessary for their control. 



Insect Protection 



All animals have enemies, and in order to survive as a group they 

 must develop means of protection against these enemies. They may 

 have protective coverings of the body that act as a discouragement to 

 predators. The hard exoskeleton of most adult insects is quite effective 

 and many soft bodied larvae, such as caterpillars, have developed prickly 

 hairs that will pierce the mouth of any bird that attempts to eat them. 



