MOTIONS OF INSECTS. 451 



concealed, instantly appear, and the laminae which terminate them being 

 separated from each other as widely as possible, they begin their march. 

 They employ their antennae, however, not as feelers to explore surround- 

 ing objects, their palpi being rather used for that purpose, but, it should 

 seem, merely to receive vibrations, or impressions from the atmosphere, to 

 which these laminae, especially in the male cock-chafers, or rather tree- 

 chafers (Melolonthee), present a considerable surface. Yet insects that 

 have filiform or setaceous antennae appear often to use them for exploring. 

 When the turnip-flea (Haltica oleracea) walks, its antennae are alternately 

 elevated and depressed. The same thing takes place with some woodlice 

 (Oniscidte), which use them as tactors, touching the surface on each side 

 with them, as they go along. This is not, however, constantly the use of 

 this kind of antennae ; for I have observed that Telephones lividus y a nar- 

 row beetle with soft elytra, common in flowers, when it walks vibrates 

 its setaceous antennae very briskly, but does not explore the surface with 

 them. The parasitic tribes of Hymenoptera, especially the minute ones, 

 when they move, vibrate these organs most intensely, and probably by 

 them discover the insect to which the law of their nature ordains that they 

 should commit their eggs ; some even using them to explore the deep holes 

 in which a grub, the appropriate food of their larva, lurks. 1 But upon 

 this subject J shall have occasion to enlarge when I treat of the senses of 

 insects. Antennas are sometimes used as legs. A gnat-like kind of bug 

 (Ploiaria vagabunda) has very short anterior legs, or rather arms ; while the 

 two posterior pair are very long. Its antennae 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 antennae 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. 2 Mr. Curtis suspects that Xyela 

 pusilla, a hymenopterous insect related to Xiphydria, uses its maxillary 

 palpi as legs. 3 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 arti- 

 culations 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 deter- 

 minate velocity, opposed to its weight more or less directly. 4 Various are 

 the organs by which these creatures 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 certain elastic ap- 

 pendages to the abdomen. 



The hind legs of many beetles are furnished with remarkably large and 

 thick thighs. Of this description are several species of weevils ; for in- 

 stance, Urchestes and Ramphus ; the whole tribe of skippers (Haltica), and 

 the spendid Asiatic tribe of Sagra 5 , &c. The object of these dispropor- 

 tioned and clumsy thighs is to allow space for more powerful muscles, by 



1 Marsham in Linn. Trans, iii. 26. 



2 De Geer, iii. 324. 5 Brit. Ent. i. t. xxx. f. 4. 

 4 Cuvier, Anat. Comp. i. 396. b Oliv. Entom. n. 90. t. i. 



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