400 FOOD OF INSECTS. 



doxical the proposition, seems actually to be a mean of 

 prolonging the life of insects. At least one such instance 

 has fallen under my own observation. The aphidivorous 

 flies, such as Syrphus Pyrastri, &c. live in the larva state 

 ten or twelve days, in the pupa state about a fortnight, 

 and as perfect insects sometimes possibly as long — the 

 whole term of their existence in summer not exceeding 

 at the very utmost six weeks. But one a , which 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 astonishment 

 alive three months after ; and it actually lived until the 

 June following without a particle of food. It had there- 

 fore existed in the larva state more than eight times as 

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

 gularly undergone its metamorphoses — which is as ex- 

 traordinary 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 pos- 

 terior pair of tubercles to the paper on which it was placed, 

 manifesting no other symptoms*of life than by moving the 



a 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. /. l-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. 



