342 TEXT-BOOK OF ZOOLOGY 



(c) The pincer-shaped mandibles cut off successive portions of the 

 leaves, which are then finely crushed by the masticatory parts of the 

 maxillse and conveyed to the mouth. Hence, the mouth parts of the 

 cockchafer, like those of all beetles, are constructed on the masticatory 

 type. 



{d) Leaves are poor in nutritive material (see Part I., p. 101, Section 1). 

 Hence, as in all vegetable-eaters, the intestine is long and wide, and 

 therefore requires considerable space for its lodgment. Accordingly, the 

 insect is plump and broad (as we find in herbivorous mammals. Contrast 

 with it the carnivorous species among beetles). 



B. Development. 



1. A few weeks after the beetle has left the earth its end approaches. 

 Previously, however, the female with the aid of its fossorial legs (see 

 Section A, 1 d) burrows several holes in the loose soil, in each of which 

 it deposits a number of eggs, which are white, and about the size of a 

 hemp-seed. A few weeks later the larvce emerge. At firBt these grubs 

 feed on tender roots, but later on stouter and firmer ones. With the 

 approach of the cold season they travel downwards to a depth where 

 frost does not penetrate and enter upon a winter sleep (owing to want of 

 food). In the following spring they once more ascend into the upper 

 strata of the soil, where food is abundant, eat their fill, moult (why?), 

 and feed anew with increased voracity. In this manner they live until 

 the summer of the third year. They then dig a hole and change to the 

 pupa condition, in which all the limbs remain free from the body. (See 

 illustration, p. 348, and contrast with pupa of lepidopterous insects.) After 

 only a few weeks passed in the quiescent stage the perfect beetle bursts 

 through the pupal skin, and, as we have seen above, comes to the surface 

 in the spring of the fourth year. (In South- Western Germany, Switzer- 

 land and France, the cockchafer, on account of the higher temperature 

 of the soil, reaches its full development by the third year.) 



If a very large number of cockchafers make their appearance in a 

 particular year, we can reckon on having another " May-bug " year in 

 the fourth (or third) year following. Naturally, this does not always 

 hold good, for the weather may turn out unfavourable to the develop- 

 ment of the larva, or some large increase in the enemies of the beetle 

 and its larva may fortunately cancel the calculation. 



2. As already seen, the larva of the cockchafer lives upon the roots of 

 plants. It therefore leads a subterranean existence, and we may naturally 

 expect it to have an entirely different structure from tlie fully-developed 

 beetle. 



