142 CLASS INSECTA. 



tends as far as their extremities, this he conceives to be the 

 issue for the acrid fluid which the scolopendrjB introduces 

 into the wound, and which causes the severe pain which is 

 felt after the bite. This aperture constitutes a relation be- 

 tween these insects and the araneida. 



The scolopendrse are very lively, and run with great agility. 

 M. Veiss compares the gait of the forked scolopendra, which 

 is one of the genus Lithobium of M. Latreille, to that of an 

 Helix, and supposes that the mechanism of their movements 

 takes place in nearly the same manner. According to him, 

 there is this difference, that the scolopendra, instead of walk- 

 ing, moves in succession a great number of feet. One set of 

 these feet operate in the line of position, while the others are 

 raised up ; the latter are quickly put to the ground, while the 

 last ones of each division are raised. All these various move- 

 ments, which follow the body, from the head to the hinder 

 extremity, produce kinds of undulations. The insect varies 

 its movements and their degree of force according to neces- 

 sity ; each foot resting on the line in which it walks, trans- 

 ports, in the same way as do the muscles of the snail, the 

 body, to the distance in which the limb can act. 



The ancients believed that the scolopendrae were repro- 

 duced in the same way as the tape-worms. But though this 

 opinion is inadmissible, it is no less certain that the mode of 

 generation in those insects yet remains a mystery. The 

 sexual organs would seem to be situated at the extremity of 

 the body. It is known that those insects moult and quit their 

 skin, in nearly the same manner that the wood-lice do. 

 Several species are found in foreign countries. 



