MOTIONS OF INSECTS. 289 



the six perfect legs. — The majority of larvrs of Lepi- 

 doptera have ten prolegs, eight being attached, a pair on 

 each, to the sixth, seventh, eighth, and ninth segments 

 of the body, and two to tlie twelfth or anal segment^. 

 The caterpillar 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 supporting the body in a posture more or less 

 erect^. Other hemigeometers, of which kind is the 

 larva of Noctua Gaimna, F.*", have only six prolegs, 

 four intermediate and two anal. The true geometers or 

 surveyors {Geometrce) have only two intermediate and 

 two anal prolegs. Many grubs of Coleoptera^ espe* 

 cially those of Staph^Uni^ Si/p/ice,, &c. which are long 

 and narrow, are furnished with a stiff joint at the anus, 

 which they bend doAvnwards and use as a prop to pre- 

 vent their body from trailing. This joint, though with- 

 out claws, may be regarded as a kind of proleg, Avhich 

 supports them v.hen they walk''; and probably may 

 assist their motion by pushing against the plane of po- 

 sition. 



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 with respect to their struc- 

 ture. I shall therefore now consider the motions of 

 pedate larva?, under ike several heads of v/alking or 

 running, jumping, climbing, and swimming. 



^ Lyonef, u!n supra, M. /. 4. " De Geer, i. 319. t. -xxv. /. 1-3. 



" Vol. T. 2d Ed. \9?>. " Dc Goer, i. 12. 40. t. i. /. S7. q. 



t.\\.f.}].e. 



VOL. II. U 



