282 INSECT TRANSFORMATIONS. 



loop about twice the diameter of his body. He re- 

 peats this process successively till he has spun forty, 

 sixty, or as many threads as he deems strong enough 

 for his cincture; and tlien throwing it over his head 

 towards the middle of his body, he proceeds to dis- 

 encumber himself of his old skin. 



As the numerous threads composing the cincture 

 are not glued together, but remain separate, it some- 

 time happens that they slip, in whole or in part, from 

 the claws of the caterpillar; and Ri aumur had one 

 which was foiled in all its efforts to repair such an 

 accident. It did not, indeed, make an}' attempt to 

 spin a fresh cincture, probably iiom its materials 

 being exhausted or from want of strength; so that 

 when it could not recover the fallen and entangled 

 threads, it collected a few of them, suspended in 

 which it cast its skin, but they, being too weak to sus- 

 tain it, gave way, and it fell and perished.* 



We will not revert in this place to the varied con- 

 trivances of those insects wliich construct coverings 

 either of silk or other materials for inclosing their 

 pupa?, sucli as the silk-worm, the puss-moth cater- 

 pillar, the tent-makers, &c; but there is one family 

 whose proceedings are so singular that they well 

 merit investigation. We refer to the numerous spe- 

 cies of what are indefinitely termed common flies, 

 {MascidcL'), and some families allied to them. Un- 

 like most other larva^, these never cast their skins, 

 not even when they chaiige into pupa?. The mag- 

 got of the con:imon blow-fly [Miisca vomiioria), for 

 example, when about to undergo its transformation, 

 quits the carcase uhere it has been feeding, and bur- 

 rows for an inch or two into the first soft earth it can 

 meet with. Here it draws in its body into a shorter 

 compass, and the soft skin being thus condensed, 



♦ Mem. sur les Insectes, vols, i, ix. 



