STATES OF INSECTS. 113 



larva be of a tolerable size, distinguished at the first view. 

 In those of many Dipterous insects, however, the head is 

 covered with the same flexible membranous skin with the 

 rest of the body, from which it is often scarcely to be di- 

 stinguished. In these, except that it contains the organs 

 of manducation, it wears no more the appearance of a 

 head than any other segment of the body, and scarcely 

 so much as the last or anal one. The head of these larvae 

 is also remai'kable for another peculiarity, — that it is ca- 

 pable of being extended or contracted, and assuming dif- 

 ferent forms at the will of the insect : a property which 

 the head of no superior animal can boast. It is probable 

 that there is a considerable variety in the shape and cir- 

 cumstances of the heads of larvae ; but since, with the ex- 

 ception of those of Lepidoptera, they have had less at- 

 tention paid to them than they deserve (indeed in a vast 

 number of cases, from the difficulty of meeting with them, 

 these variations, except in a few instances, have not been 

 described), I will here mention a few of the most remark- 

 able. The head of the young larva at its first exclusion 

 from the egg is usually the most dilated part of the body, 

 but it does not often continue so. In that of Cicindeld 

 campestris, however, — the beautiful green beetle some- 

 times found in sandy banks, — and also in several cater- 

 pillars of Lepidoptera, it is much larger than any of the 

 following segments 3 ; which, in conjunction with the 

 animal's formidable jaws, gives it a most ferocious ap- 

 pearance. In some lepidopterous larvae the head is of 

 the same diameter with the rest of the body, but in in- 

 sects in general it may, I think, be stated as less ; and 



» Plate XVII. Fig. 13. 

 VOL, III. I 



