440 MOTIONS OF INSECTS. 



their points outwards. Thus they can lay stronger hold of the plane of 

 position. * 



The number of these prolegs varies in different species and families. In 

 the numerous tribes of saw-flies (Seirifera), the larvae of which resemble 

 those Lepidoptera, and are called by Reaumur spurious caterpillars (fausses 

 chenilles), one family (Lophyrus) has sixteen prolegs ; a second (Hylotoma, 

 &c.) fourteen; another (Tenthredo 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. 2 The caterpillar of the puss-moth (Centra 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. 3 Other hemigeometers, 

 of which kind is the larva of Plusia Gamma, have only six prolegs, four inter- 

 mediate and two anal. The true geometers or surveyors (Geometrce) have 

 only two intermediate and two anal prolegs. Many grubs of Coleoptera, 

 especially those of Staphylinidce, Silphidce, &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 4 ; and probably may assist their motion by pushing against the 

 plane of position. 



With respect to the larvae 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 

 Iarva3, 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 Filipendulce) 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. 5 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 6 ) 

 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 



1' Lyonet, 82. t iii. f. 1016. 3 Ibid. 1. 1. f. 4. 



s De Geer, i. 379. t. xxv. f. 1. 3. 



Ibid. i. 12. 40. t. i. f. 27. q. t. vi. f. 11. e. 



* Ibid. i. 424. 6 Kirby in Linn. Trans, v. 258. 



