62 ZOOLOGY 



have said : " The function of the Cerarabycirlse is to hold the 

 vegetable world in check by destroying woody fibre; the Bru- 

 chidiB (weevils) effect a similar result by attacking the seeds ; 

 and the Chrysomehdte by destroying the leaves." 



The geographical range of beetles is likewise great. They 

 penetrate to the tops of the highest mountains. They are 

 found on the most arid deserts, where they attain ver}^ great 

 size and ver\' great hardness. While they reach their greatest 

 abundance in the heavily forested tropics, the}' are found in 

 extreme nortliern lands. 



During develo]3ment beetles, like Lepidoptera anfl Hjanen- 

 optera, undergo great change in form. As an illustration we 

 will consider the development of the Colorado Potato-beetle. 

 In this species the orange-colored eggs are laid often in a very 

 regular manner on the under side of the potato leaf. Here 

 they develop for several days. In about a week, however, 

 the young, reddish, black-spotted larva, or " grub," comes out. 

 Like the adult beetle, it has three pairs of thoracic legs. After 

 feeding actively for two or three weeks, the larva descends 

 into the ground, forms a naked yellow pupa, and emerges in 

 about ten days as an adult. From two to four l)roods are 

 prorluced during the year. The adult beetles spend the winter 

 in the ground, crawling forth and laying eggs the following 

 spring (cf. Fig. 65 a). 



The habits of the larvce of the different kinds of beetles are 

 as varied as those of the adults. Some of the larvas live in 

 the ground mth their jaws exposed in wait for ]irey. Many 

 wander about to seek food either on land or under water. 

 Others eat the wood in which thev are embedded, while still 

 others are nourished by the ball of carrion in which the mother 

 has deposited her eggs. 



