INSECTS 335 



namely, the head, thorax (or chest), and the abdomen. The rest 

 of the Arthropoda are not so consistently divided. 



Other general characteristics of the group are, that their muscles 

 are attached to the inside of their external covering, which, being 

 firm, is their main support; that they do not breathe by means of 

 gills or lungs, but through breathing-holes placed along the sides of 

 the abdomen, by which air is conveyed to all parts of their bodies; 

 and that their heads are furnished with very sensitive feelers. 



Insects as they grow pass through a number of changes in form 

 before they reach maturity. When they are hatched from the egg 

 they are tiny caterpillars or grubs. While in this form they have 

 voracious appetites, for they are continually eating. This is neces- 

 sary, for they grow very quickly, so quickly, indeed, that their skin 

 several times becomes too small for them, and they cast it off and 

 appear in a nice new coat. When they have grown to their full 

 size, some of them make a nest called a cocoon, into which they 

 retire for a longer or shorter period. Here they change their form 

 completely, and become what is known as a chrysalis. You would 

 scarcely believe by the appearance alone that the caterpillar and 

 the chrysalis were the same creature ; for the latter has no legs and 

 no apparent head. It is just a something within a stiff shell. But 

 as the days pass a new form is shaping itself inside; and one 

 morning you will find that a beautiful moth or butterfly has broken 

 its way out of the shell. At first the wings are not fully formed, 

 but they soon stretch to their full size and their owner flies away. 

 It is difficult to realize that this is the same creature as the little 

 worm-like caterpillar you saw hatched from the egg. 



It seems hard that, after taking so much trouble to get wings 

 and be able to fly, it should only have a very short time to live. 

 But most insects when they reach maturity only live a few days, 

 although some live for several weeks, and occasionally hibernate 

 through the winter. They lay their eggs in a place of safety, and 

 where there will be plenty of food for the young caterpillars, and 

 then they die. 



Some insects pass the first part of their lives in water, and the 

 latter part in the air; while others spend most of their time in the 

 water. 



