222 



MOTIONS OF INSECTS. 



I shall begin the list of walkers, the movements of which 

 are aided by various instruments, with one which is well 

 known to most people, — the grub of the nut-weevil (Ba- 

 laninus Nucum). When placed upon a table, after lying 

 some time, perhaps, bent in a bow, with its head touching its 

 tail, at last it begins to move, which, though in no certain 

 direction, it does with more speed than might be expected. 

 Kosel fancied that this animal had feet furnished with claws ; 

 but in this, as De Geer justly observes, he was altogether 

 mistaken, since it has not the least rudiment of them, its 

 motion being produced solely by the alternate contraction 

 and extension of the segments of the body, assisted, perhaps, 

 by the fleshy prominences of its sides. Other larvse have 

 this annular motion aided by a slimy secretion, which gives 

 them further hold upon the plane on which they are moving, 

 and supplies in some degree the place of legs or claws. 

 That of the weevil of the common figwort (Cionus Scrophu- 

 larice) is always covered with slime, which enables it, though 

 it renders its appearance disgusting, to walk with steadiness, 

 by the mere lengthening and shortening of its segments, upon 

 the leaves of that plant. 1 Of this kind, also, are those larva?, 

 mentioned above, received by De Greer from M. Ziervogel, 

 which, adhering to each other by a slimy secretion, glide 

 along so slowly upon the ground as to be a quarter of an 

 hour in going the breadth of the hand, whence the natives 

 call their bands Gards-drag? 



As a further help, others again call in the assistance of 

 their unguiform mandibles. These, which are peculiar to 

 grubs with a variable membranaceous, or rather retractile 

 head 3 , especially those of the fly tribe {Muscidoz), when the 

 animal does not use them, are retracted not only within the 

 head, but even within the segments behind it 4 ; but when it 

 is moving, they are protruded, and lay hold of the surface on 

 which it is placed. They were long ago noticed by the 

 accurate Ray. " This blackness in the head," says he, 

 speaking of the maggot of the common flesh-fly, " is caused 



i De Geer, v. 210. 2 Ibid. vi. 338. 



3 See MacLeay in Philos, Mag. &c. N. Ser. No. 9. 178. 



4 De Geer, vi. 65. 



