MOTIONS OP INSECTS. 



227 



produces a grub inhabiting the water -hemlock, which has 

 only six tubercles that occupy the place and are representa- 

 tives of the legs of the perfect insect. 1 



Some larva? have these tubercles armed with claws. The 

 maggot of a fly described by De Greer ( Volucella plumata) 

 has six pair of them, each of which has three long claws. 

 This animal has a radiated anus, and seems related to those 

 flies that live in the nests of humble-bees. 2 



Insects, in the peculiarities of their structure, as we have 

 seen in many instances, sometimes realise the wildest fictions 

 of the imagination. Should a traveller tell you that he had 

 seen a quadruped whose legs were on its back, you would 

 immediately conclude that he was playing upon your credu- 

 lity, and had lost all regard to truth. What then will you 

 say to me, when I affirm, upon the evidence of two most un- 

 exceptionable witnesses, Reaumur and De Geer, that there are 

 insects which exhibit this extraordinary structure ? The grub 

 of a little gall-fly, appearing to be Cynips Quercus inferus of 

 Linne, which inhabits a ligneous gall resembling a berry to 

 be met with on the underside of oak-leaves, was found by 

 the former to have on its back, on the middle of each seg- 

 ment, a retractile fleshy protuberance that resembled strikingly 

 the spurious legs of some caterpillars. A little attention will 

 convince any one, argues Reaumur, that the legs of insects 

 circumstanced like the one under consideration, if it has any, 

 should be on its back. For this grub, inhabiting a spherical 

 cavity, in which it lies rolled up as it were in a ring, when 

 it wants to move, will be enabled to do so, in this hollow 

 sphere, with much more facility, by means of legs on the 

 middle of its back, than if they were in their ordinary 

 situation. 3 So wisely has Providence ordered every thing. 

 Another similar instance is recorded by De Geer, which in- 

 deed had previously been noticed, though cursorily, by the 

 illustrious Frenchman. 4 There is a little larva, he observes, 

 to be found at all seasons of the year, the depth of winter 

 excepted, in stagnant waters, which keeps its body always 



1 De Geer, v. 228. 2 Ibid. vi. 137. t. viii. f. 8, 9. 



3 Reaura. iii. 496. t. xlv. f. 3. 



4 Ibid. Mem. de VAcad. Roy. des Sciences de Paris, An. 1714. p. 203. 



Q 2 



