336 



FOOT) OF INSECTS. 



one^ wliicli I put under a glass on the 2d of June, 1811, 

 when about half grown, and, after supplying it with Aphides 

 once or twice, by accident forgot, I found, to my great as- 

 tonishment, alive three months after ; and it actually lived 

 until the June following without a particle of food. It had, 

 therefore, existed in the larva state more than eight times as 

 long as it would have lived in all its states, if it had regularly 

 undergone its metamorphoses, which is as extraordinary a 

 prolongation of life as if a man were to live 560 years. It is 

 true that its existence was not worth having even to the 

 larva of a fly. For the last eight months it remained without 

 motion, attached by its posterior pair of tubercles to the 

 paper on which it was placed, manifesting no other symptoms 

 of life than by moving the fore part of the body when 

 touched, and replacing itself on its belly if turned upon its 

 back. But this was quite enough to prove it still alive. I 

 can attribute this singular result to no other circumstance 

 than its having been deprived of a sufficient quantity of food 

 to bring it into the pupa state, though provided with enough 

 for the attainment of nearly its full growth as larva. 

 Possibly the same remote cause might act in this case, as 

 operates to prolong the term of existence of annual plants 

 that have been prevented from perfecting their seed ; and it 

 would almost seem to favour the hypothesis of some physiolo- 

 gists, who contend that every organised being has a certain 

 portion of irritability originally imparted to it, and that its 

 life will be long or short as this is slowly or rapidly excited 

 — no great consolation this for the advocates for fast-living, 

 unless they are in good earnest in their affected preference of 

 a " short life and a merry one ; " though it must be admitted 

 that they would have the best of the argument, were the 



1 Not having ever met with another specimen, I am unable to say of what 

 precise species of aphidivorous fly it is the larva ; nor can I find a figure of it, 

 though it approaches near to one given by De Geer (vi. t. 7. f. 1 — 3.). Its 

 shape is oblong-oval, length about four lines, and colour pale red speckled with 

 black. Each of the seven or eight segments which compose the body projects 

 on each side into three serrated flat aculei or teeth ; three or four similar but 

 smaller aculei arm the head ; and two, much larger than the rest, the anus, one 

 on each side of the usual bifid protuberance which bears the respiratory plates. 

 A bifid tubercular elevation is also placed in the middle of the back of each 

 segment. 



