MOTIONS OF INSECTS. 435 



tribe, figured by Reaumur, is thus circumstanced. In this case the pro- 

 cesses in question proceed from the head, and are armed with claws. 1 

 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 the 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 ser- 

 pent, 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, tenta- 

 cula. They resemble, by their length and rigidity, wooden legs. The an- 

 terior leg is attached to the under side, 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, 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 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. 2 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 them, the common base, from which the feet are branches, was retracted 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. 3 



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

 is supplied by fleshy and often retractile mamillae 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. 4 A subcu- 

 taneous larva belonging to the same order, that mines the leaves of the 

 rose, moves also by tubercular legs assisted by slime. It has eighteen 

 homogeneous legs, with which, when removed from its house of conceal- 

 ment, it will walk well upon any surface, whether horizontal, inclined, or 

 even vertical. 6 But the greatest number of legs of this kind that distin- 

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

 (Sc&va Pyrastri) that devours the Aphides of the rose. This animal has 

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

 seven, making in all forty-two. 6 The grub of the weevil of the dock 



1 Reaum. v. t. vi. f. 5. m m. 



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

 culated 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. 



3 Lesser, 1. i. 96. note f. 4 Klemann, Beitrage, 324. 



5 De Geer, i. 447. t. xxxi. f. 17. Ibid. vi. 111. 



FF 2 



