INSECTS 255 



INSECTS 



231 Importance of Insects. Insects seem to be the 

 form of life that is peculiarly adapted to this world. About 

 95 per cent of all kinds of animals are insects. In actual 

 numbers of individuals they are still more in the lead. 

 Many of these insects live at our expense, and in spite of 

 our efforts to subdue them. The cotton-boll weevil, chinch- 

 bug, grasshopper, San Jose scale, codling moth, potato 

 beetle, and many others are well-known crop pests. It has 

 been estimated that insects destroy about $700,000,000 

 worth of crops per year in the United States. It is well 

 worth while for the farmer to learn something of the life 

 and habits of insects, in order that he may prevent some 

 of this loss. 



However, we must not come to think of all insects as 

 harmful; many of them are very useful. Bees are the first 

 of which we think. These and other insects are of use in 

 carrying the pollen for certain crops. Other insects are 

 useful because they live on the harmful kinds. 



232. What an Insect Is. All insects have six legs in 

 their mature stage. This feature distinguishes them from 

 spiders, which have eight legs, and from millipedes and 

 centipedes, which have many legs. A caterpillar appears 

 to have more than six legs, but those at the rear end are 

 not true legs, as will be seen by examining one. When 

 the caterpillar changes to a butterfly or moth, only the 

 six true legs remain. 



The body of an insect is divided into three parts that 

 are usually quite apparent: head, thorax and abdomen. 

 A wasp shows these parts very clearly. 



