MOTIONS OF INSECTS. 



251 



tremity, which is rather thick, is made to rest upon the sur- 

 face on which the animal moves, and so supply the place of 

 fore-legs. 1 Mr. Curtis suspects that Xyela pusilla, a hymen- 

 opterous insect related to Xiphydria, uses its maxillary palpi 

 as legs. 2 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 en- 

 dowed 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 determinate velocity, opposed to its weight more 

 or less directly. 3 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 appendages to the abdomen. 



The hind legs of many beetles are furnished with remark- 

 ably large and thick thighs. Of this description are several 

 species of weevils ; for instance, Orchestes and Ramphus ; the 

 whole tribe of skippers (Haltica), and the splendid Asiatic 

 tribe of Sagra 4 , &c. The object of these disproportioned 

 and clumsy thighs is to allow space for more powerful mus- 

 cles, by which the tibia?, when the legs are unbent, are im- 

 pelled with greater force. In the Orthoptera order all the 

 grasshoppers, including the genera Gryllotalpa, Gryllus, 

 Tridactylus, Locusta, Acrida, Pterophylla, Pneumora, Trux* 

 alis, Acrydium, Tetrix, &c, are distinguished by incras- 

 sated posterior thighs ; which, however, are much longer, 

 more tapering and shapely (they are indeed somewhat 

 clumsy in the two first genera, the crickets), than those of 

 most of the Coleoptera that are furnished with them. When 

 disposed to leap, these insects bend their hind leg so as to 



i De Geer, iii. 324. 



3 Cuvier, Anat. Comp. i. 396. 



2 Brit. Ent. i. t. xxx. f. 4, 

 4 Oliv. Entom. n. 90. t. i. 



