ARTHROPODA. 



247 



stored grains of various kinds ; numerous beetles lay their 

 eggs in wood, dead or living, and their larvae eat their 

 way in tunnels through the solid timber. It sometimes 

 takes these larvae four or five years to mature, and 

 thus they are able, in getting their nutrition, to do a 

 great amount of damage. With these are to be included 

 the fire-flies, the scarabs or dung beetles, the June bugs, 

 and some water beetles which may be seen whirling 

 about at the surface of ponds or diving beneath it. 



Many of the beetles are brilliantly colored, and for this 

 reason are often collected by young students. It is 

 thought that these colors may, in some instances at least, 

 be of direct value to the animals. 



FIG. 93. The army-worm (Leucania unipuncta). 

 B, adult moth. 



After Riley. A, caterpillar; 



Questions on the Figure. What are the principal facts con- 

 cerning the habits and economic importance of the army- worm? 

 Why is it so called? 



263. The Lepidoptera (Butterflies and Moths). These 

 are the most conspicuous and best known of the insects. 

 They are found all over the world and are so various in 

 size, color, and habits as to be one of the most interesting 

 groups of animals for popular study. The mouth parts 

 are enlongated into a proboscis for sucking the nectar of 

 flowers. They pass through a complete metamorphosis, 



