448 MOTIONS OF INSECTS. 



(vibrans) from the constant vibration which, when reposing, it imparts to 

 its wings. This motion, also, I have reason to think, assists its respira- 

 tion. Some insects when awake are very active with their antennas, 

 though their bodies are at rest. I remember one evening attending for 

 some time to the proceedings of one of those caseworm-flies (Leptocerus) , 

 that are remarkable, like certain moths, for their long antennas. It was 

 perched upon a blade of grass, and kept moving these organs, which were 

 twice as long as itself, in all directions, as if by means of them it was 

 exploring every thing that occurred in its vicinity. Many Tipulge, and 

 likewise some mites (Acarus vibrans and Gamasus motatorius) t distinguished 

 by long anterior legs, from this circumstance denominated pedes motatorii 

 by Linne, holding them up in the air impart to them a vibratory motion, 

 resembling that of the antennae of some insects. 1 I scarcely need mention, 

 what must often have attracted your attention, the actions of flies when 

 they clean themselves ; how busily they rub and wipe their head and 

 thorax with their fore legs, and their wings and abdomen with their hind 

 ones. Perhaps you are not equally aware of the use to which the rove- 

 beetles (Staphylinus L.) put their long abdomen. They turn it over their 

 back not only to put themselves in a threatening attitude, as I lately re- 

 lated, but also to fold up their wings with it, and pack them under their 

 short elytra. 



With respect to the motions of insects in action, they may be subdivided, 

 as was just observed, into motions whose object is change of place and 

 sportive motions. 



The locomotions of these animals are walking, running, jumping, climbing, 

 flying, swimming, and burrowing. I begin with the walkers. 



The mode of their walking depends upon the number and kind of their 

 legs. With regard to these, insects may be divided into four classes ; viz. 

 Hexapods, or those that have only six legs : such are those of every order 

 except the Aptera of Linne, of which only three or four genera belong to 

 this class ; Octopods, or those that have eight legs, including the tribes of 

 mites (Acarina) ; spiders (^Araneidce) ; long-legged spiders (Phalangidce) ; 

 and scorpions (Scorpinnidce) : Polypods, or those that have fourteen legs, 

 consisting of the wood-lice tribe (Oniscida;) ; and Myriapods, or those 

 that have more than fourteen legs often more than a hundred com- 

 posed of the two tribes of centipedes (Scolopendridce) and millepedes 

 (lulidee). The first of these classes may be denominated proper, and the 

 rest improper insects. The legs of all seem to consist of the same general 

 parts ; the hip, trochanter, thigh, shank, and foot ; the four first being 

 usually without joints (though in the Araneid<z, &c. the shank has two), 

 and the foot having from one to above forty. 2 



1 De Geer, vi. 335. 



2 The most common number of joints in the tarsus is from two to five; but the 

 Phalangidae have sometimes more than forty. In these, under a lens, this part 

 looks like a jointed antenna. 



Geoffroy, and after him most modern entomologists, has taken the primary 

 divisions of the Cokoptera order from the number of joints in the tarsus ; but this, 

 although perhaps in the majority of cases it may afford a natural division, will not 

 universally. For not to mention the instance of Pselaphus, clearly belonging to 

 the Brachyptera both Oxytelus Grav., and another genus that I have separated 

 from it (Carpalimus K. Ms.), have only two joints in their tarsi. In this tribe, 

 therefore, it can only be used for secondary divisions. K. 



