COLEOPTERA, OR BEETLES. 63 



biting structure in full perfection^ and if so^ we shall 

 not be disappointed. All the parts already described 

 as characteristic of the biting mouth are here present 

 in ftdl perfection^ — the mandibles are usually powerful 

 horny organs, and the maxillse are well developed, 

 generally horny, frequently toothed, and always fur- 

 nished with jointed palpi. The labrum or upper lip, 

 although often of small size, is generally distinctly 

 perceptible in the form of a horny plate, of variable 

 form according to the species, closing the space 

 between the bases of the mandibles; occasionally, 

 however, this organ is concealed beneath a projecting 

 portion of the front of the head. The labium or 

 lower lip, on the contrary, is always of considerable 

 size, and provided with a pair of jointed palpi of 

 moderate length. In the details of their structure, 

 as a matter of course, the parts of the mouth vary 

 considerably in accordance with the habits of the 

 insects and the nature of their food; these differ- 

 ences are of the greatest importance in the classifica- 

 tion of the immense number of species included in 

 the order, and we shall have occasion to notice some 

 of them as we proceed. 



Another character of primary importance presented 

 by the insects of the order Coleoptera consists in their 

 complete metamorphosis. They quit the egg in the 

 form of a grub, which is always furnished with a 

 horny head, although the segments of the body are 

 frequently quite destitute of feet. Their food in 

 this condition is as various as in the perfect state; 

 it consists sometimes of animal, and sometimes of 

 vegetable matters, sometimes in a fresh or living 

 state, and sometimes in a condition of putrefaction or 

 decay. A considerable number live in dung, espe- 



