MOTIONS OF INSECTS. 433 
I shall begin the list of walkers, the movements of which are aided by 
yatious instruments, with one which is well known to most people, — the 
grub of the nut-weevil (Balaninus Nucum). When placed upon a table, 
ater 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. Résel 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 larve have this annular motion aided by a slimy secre- 
tion, 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 Scrophulariz) 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. Of this kind, also, are those 
larvae, mentioned above, received by De Geer 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 membrana- 
ceous, or rather retractile head’, especially those of the fly tribe (AZuscide), 
when the animal does not use them, are retracted not only within the head, 
but even within the segments behind it*; 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 by 
two black spines or hooks, which when in motion it puts forth, and fixing 
them in the ground, so drags along its body.”® The larvae of the aphidi- 
vorous flies (Sceva, &c.), the ravages of which amongst the Aphides I have 
before described to you, transport themselves from place to place in the 
same way, walking by means of their teeth. Fixing their hind part to the 
substances on which they are moving, they give their body its greatest 
possible tension ; and, if I may so speak, thus take as long a step as they 
can: next laying hold of it with their mandibles, by setting free the tail, 
and relaxing the tension, the former is brought near the head. Thus the 
animal proceeds, and thus will even walk upon glass. Some grubs, as 
those of the lesser house-fly (Anthomyia canicularis), have only one of these 
claw-teeth ; and in some they have the form as well as the office of legs.* 
Bonnet mentions an apodous larva, that, before it can use its mandibles, is 
obliged to spin, at certain intervals, little hillocks or steps of silk, of which 
it then lays hold by them, and so drags itself along. 
Besides their mandibular hooks, some of these grubs supply the want of 
1 De Geer, v. 210. 2 Ibid. vi. 338. 
5 See MacLeay in Philos. Mag. &c., N. Ser. No. 9. 178. 
4 De Geer, vi. 65. 
5 Hist. Ins, 270. © Reaumur, iii. 369, 
7 De Geer, vi. 76. Reaumur, iy. 876. Swamm Bibl. Nat. Ed, Hill, ii, 46. a. t 
XxXxix, f. 3. bh. he 
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