276 MOTIONS OF INSECTS. 



These feet, like the tentacula of snails, are retractile 

 within the leg, and even within the body, so that only a 

 little stump, as it were, remains without. The insect 

 moves them both together, as a lame man does his 

 crutches, either backwards or forwards. The two pos- 

 terior legs are placed at the anal end of the body. They 

 are similar to the one just described, but larger, and 

 entirely separate from each other, being not, like them, 

 retractile within the body, but always stiff and extended. 

 These also are armed with hooks. In walking, this larva 

 uses these two legs much as the caterpillars of the moths, 

 called Geometry do theirs. By the inflection of the 

 anus it can give them any kind of lateral movement, ex- 

 cept that it can neither bend nor shorten them, since like 

 a wooden leg, as I have before observed, they always re- 

 main stiff and extended a . Lyonet had observed this larva, 

 or a species nearly related to it; but he speaks of it as 

 having four legs, two before and two behind. Probably, 

 when he examined them, the common base, from which 

 the feet are branches, was retracted within the body b . 



Generally speaking, however, in these apodous walk- 

 ers the place of legs is supplied by fleshy and often re- 

 tractile mamillae or tubercles. By means of these and a 

 slimy secretion, unaided by mandibular hooks, the ca- 

 terpillar of a little moth (Apoda Testudo,} moves from, 

 place to place . A subcutaneous larva belonging to the 

 same order, that mines the leaves of the rose, moves 



a De Geer, vi. 395. PLATE XXIII. FIG. 7. Foreleg, a. Hind- 

 legs, bb. Mr. W. S. MacLeay is of opinion that these legs are pe- 

 cundulated spiracles, (Philos. Mag. N. Series, No. 9. 178.) but it is 

 evident from De Geer's account that the animal uses them as legs, 

 and like legs they are armed with hooks or claws. 



b Lesser L. i. 96. note f. c Klemann, Bcitrage, 324. 



