H.j METAMORPHOSES OF INSECTS. 27 



CHAPTER II. 





THE INFLUENCE OF EXTERNAL CONDITIONS 

 ON THE FORM AND STRUCTURE OF LARVAE. 



THE facts recapitulated briefly in the preceding 

 chapter show, that the forms of insect larvae depend 

 greatly on the group to which they belong. Thus 

 the same tree may harbour larvae of Diptera, 

 Hymenoptera, Coleoptera, and Lepidoptera ; each 

 presenting the form typical of the family to which 

 it belongs. 



If, again, we take a group, such, for instance, as 

 the Lamellicorn beetles, we shall find larvae extremely 

 similar in form, yet very different in habits. Those, 

 for instance, of the common cockchafer (Fig. i) feed 

 on the roots of grass ; those of Cetonia aurata (Fig. 2) 

 inhabit ants' nests ; the larvae of the genus Trox 

 (Fig. 3) are found on dry animal substances ; of 

 Oryctes (Fig. 4) in tan-pits ; of Aphodius (Fig. 5) in 

 dung ; of Lucanus (the stag-beetle, Fig. 6) in wood. 



On the other hand, in the present chapter it will be 

 m)' object to show that the form of the larva depends 

 very much on the conditions of its life. Thus, those 

 larvae which are internal parasites, whether in animals 



