MOTIONS OF INSECTS. 289 
vus, Latr.) has sixteen prolegs; a second (Hylotoma, 
Latr. &c.) fourteen; another (Tenthredo, ¥.) twelve; 
and a fourth (Zyda, TF.) none at all, having only the six 
perfect legs. The majority of larva 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 ca- 
terpillar of the puss-moth (P. Bombyx Vinula, L.) and 
some others, instead of the anal prolegs, have two tails 
or horns. A hemigeometer, 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 sup- 
porting the body in a posture more or less erect”. Other 
hemigeometers, of which kind is the larva of Noctua 
Gamma, F.°, have only six prolegs, four intermediate 
and two anal. ‘The true geometers or surveyors (Geo- 
metre) have only two intermediate and two anal prolegs. 
Many grubs of Coleoptera, especially those of Staphylinz, 
Silphe, &c., which are long and narrow, are furnished 
with a stiff joint at the anus, which they bend down- 
wards and use as a prop to prevent their body from trail- 
ing. This joint, though without claws, may be regarded 
as a kind of proleg, which supports them when they 
walk4; and probably may assist their motion by ee 
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 larvee, un- 
aLyonet, ubi supr.t.1.f.4. © De Geer, i. 379. ¢. xxv. f 1. 3. 
© Vor. I. 4th Ed. 190, 191. 4 De Geer, i. 12, 40. t. 1. fi 27. 9. 
EN. fo Vice. 
VOL, I. U 
