MOTIONS OF INSECTS. 313 
in which a grub, the appropriate food of their larvay 
lurks*. But upon this subject I shall have occasion to 
enlarge when I treat of the senses of insects—Antennze 
are sometimes used as legs. A gnat-like kind of bug 
(Gerris vagabundus, F.) has very short anterior legs; 
or rather arms, while the two posterior pair are very 
long. Its antennz also are long. When it walks, 
which it does very slowly, with a solemn measured step, 
its fore legs, which perhaps are useful only in climbing, 
or to seize its prey, are applied to the body, and the 
antennz being bent, their extremity, which is rather 
thick, is made to rest upon the surface on which the 
animal moves, and so supply the place of fore legs®.— 
I have observed that mites often use the long hairs with 
which the tail of some species is furnished, to assist them 
in walking. 
Another mode of motion with which many insects are 
endowed is jumping. ‘This is generally the result of the 
sudden unbending of the articulations of the posterior 
legs and other organs, which before had received more 
than their natural bend. ‘This unbending impresses a 
violent rotatory motion upon these parts, the impulse of 
which being communicated to the centre of gravity, 
causes the animal to spring into the air with a determi- 
nate velocity, opposed to its weight more or less di- 
rectly°. Various are the organs by which these crea- 
tures are enabled to effect this motion. The majority do 
it by a peculiar conformation of the hind legs; others, by 
a pectoral process; and others, again, by means of cer- 
tain elastic appendages to the abdomen. 
4 Marsham in Ling. Trans. tii. 26— b De Geer, 11. 324— 
© Cuvier, Anat. Comp. 1. 496— 
