440 MOTIONS OF INSECTS. 
their points outwards. Thus they can lay stronger hold of the plane of 
Osition.* 
: The number of these prolegs varies in different species and families. Tp 
the numerous tribes of saw-flies (Servifera), the larvae of which resemble 
those Lepidoptera, and are called by Reaumur spurious caterpillars ( fausses 
chenilles), one family (Lophyrus) has sixteen prolegs ; a second (/Iy/otoma, 
&c.) fourteen ; another (Zenthredo F.) twelve ; and a fourth (Lyda) none 
at all, having only the six perfect legs. The majority of larvae of Lepidoptera 
have ten prolegs, eight being attached, a pair on each, to the sixth, seventh, 
eighth, and ninth segments of the body, and two to the twelfth or anal 
segment.” The caterpillar of the puss-moth (Cerura Vinula) and some 
others, instead of the anal prolegs, have two tails or horns, A hemi- 
geometer, described by De Geer, has only six intermediate prolegs, the 
posterior pair of which are longer than the rest, to assist the anal pair in 
supporting the body in a posture more or less erect.’ Other hemigeometers, 
of which kind is the larva of Plusia Gamma, have only six prolegs, four inter- 
mediate and twoanal. The true geometers or surveyors (Geometr@) haye 
only two intermediate and two anal prolegs. Many grubs of Coleoptera, 
especially those of Staphylinide, Silphide, &c., which are long and narrow, 
are furnished with a stiff joint at the anus, which they bend downwards and 
use as a prop to prevent their body from trailing, This joint, though with- 
out claws, may be regarded as a kind of proleg, which supports them when 
they walk*; and probably may assist their motion by pushing against the 
plane of position. 
With respect to the larva that have only perfect legs, having just given 
you an account of these organs, I have nothing more to state relating to 
their structure. I shall therefore now consider the motions of pedate 
larva, under the several heads of walking or running, jumping, climbing, 
and swimming. 
Amongst those that walk, some are remarkable for the slowness of their 
motion, while others are extremely swift. The caterpillar of the hawk-moth 
of the Filipendula (Zygena Filipendule) is of the former description, moving 
in the most leisurely manner; while that of Apatela leporina, a moth un- 
known in Britain, is named after the hare, from its great speed. The 
caterpillar of another moth, the species of which seems not to be ascertained, 
is celebrated by De Geer for the wonderful celerity of its motions. When 
touched it darts away backwards as well as forwards, giving its body an 
undulating motion with such force and rapidity, that it seems to fly from 
side to side. Cuvier observes, that the grubs of some coleopterous and 
neuropterous insects, which have only the six perfect legs, by means of 
them lay hold of any surrounding object, and, fixing themselves to it, drag 
the rest of their body to that point; and that those of many capricorn 
beetles and their affinities (but that of Callidium violaceum is an apode®) 
have these legs excessively minute and almost nothing; that they move in 
the sinuosities which they bore by the assistance of their mandibles, with 
which they fix themselves, and also of several dorsal and ventral tubercles, 
by which they are supported against the sides of their cavity, and push 
! Lyonet, 82. t, iii. f. 10—16, 9 Thid. t. i. f. 4. 
5 De Geer, i. 879. t. xxv. f. 1. 8, 
4 Ibid. i, 12. 40. t i. f. 27. q. t. vie f, 11. 
5 Ibid. i, 424, 6 Kirby in Linn, Trans. y. 258. 
