470 MOTIONS OF INSECTS. 



anterior extremity by a pair of spurious legs. An aquatic larva of a most 

 singular form, and of the same tribe, figured by Reaumur, is thus circum- 

 stanced. In this case the processes in question proceed from the head, 

 and are armed with claws.^ Would you think it — another Tipularian 

 grub is distinguished by three, legs of this kind ? It was first noticed by 

 De Geer under the name of Tipula maculata {Tanypus monilis Meig.), 

 who gives the following account of its motions and their organs : — It is 

 found, he observes, in liie water of swampy places and in ditches, is not 

 bigger than a horse-hair, and about a quarter of an inch in length. Its 

 mode of swimming is like that of a serpent, with an undulating motion 

 of the body, and it sometimes walks at the bottom of the water, and upon 

 aquatic plants. The most remarkable part of it are its legs, called by 

 Latreille, but it should seem improperly, tentacula. They resemble, by 

 their length and rigidity, wooden legs. The anterior leg is attached to 

 the underside, but towards the head, of the first segment of the body. It 

 is long and cylindrical, placed perpendicularly or obliquely, according to 

 the different movements the animal gives it, and terminates in two feet, 

 armed at their extremity by a coronet of long moveable hooks. 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 posterior 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, retrac- 

 tile 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 cater- 

 pillars of the moths, called Geometrce, do theirs. By the inflection of the 

 anus it can give them any kind of lateral movement, except that it can 

 neither bend nor shorten them, since like a wooden leg, as I have before 

 observed, they always remain stiff and extended.^ 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 then%, 

 the common base, from which the feet are branches, was retracted within 

 the body.^ 



Generally speaking, however, in these apodous walkers the place of 

 leffs is supplied by fleshy and often retractile mamillse or tubercles. By 

 means of these and a slimy secretion, unaided by mandibular hooks, the 

 caterpillar 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 also by tubercular legs assisted by slime. It has 

 ei^^hteen homogenous legs, with which, when removed from its house of 

 concealment, it will walk well upon any surface, whether horizontal, 

 inclined, or even vertical.^ But the greatest number of legs of this kind 

 that distinguish any known larva is to be observed in that of a two-winged 

 fly (Scava Pyrastri) that devours the Aphides of the rose. This animal 

 has six rows of tubercular feet, with which it moves, each row consisting 



» Reauni. v. t. vi. f. 5. m. m. 



2 De Geer, vi. 395. Mr. W. S. MacLeay is of opinion that these legs are pedunculated 

 spiracles (Philos. Mas,. 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 vviih hooks or claws. 



3 Lesser, 1. i. 96. note f. * Klemann, Beicrage, 324. * De Geer, i. 447. t. xxxi. f. 17. 



