MOTIONS OF INSECTS. 



221 



Apodous larvae seldom have occasion to take long journeys; 

 and many of them, except when about to assume the pupa, 

 only want to change their place or posture, and to follow 

 their food in the substance, whether animal or vegetable, to 

 which, when included in the egg, the parent insect committed 

 them. Legs, therefore, would be of no great use to them, 

 and to these last a considerable impediment. They are 

 capable of three kinds of motion ; they either walk, or jump, 

 or swim. I use walking in an improper sense, for want of a 

 better term equally comprehensive : for some may be said to 

 move by gliding, and others (I mean those that, fixing the 

 head to any point, bring the tail up to it, and so proceed) 

 by stepping. 



The motion of serpents was ascribed by some of the 

 ancients (who were unable to conceive that it could be 

 effected naturally, unless by the aid of legs, wings, or fins,) 

 to a preternatural cause. It was supposed to resemble the 

 "incessus deorum" and procured to these animals, amongst 

 other causes, one of the highest and most honourable ranks 

 in the emblematical class of their false divinities. 1 Had they 

 known Sir Joseph Banks's discovery, that some serpents 

 push themselves along by the points of their ribs, which Sir 

 E. Home found to be curiously constructed for this purpose, 

 their wonder would have been diminished, and their serpent- 

 gods undeified. But though serpents can no longer make 

 good their claim to motion more deorum, some insects may 

 take their places ; for there are numbers of larvse that having 

 neither legs, nor ribs, nor any other points by which they 

 can push themselves forward on a plane, glide along by the 

 alternate contraction and extension of the segments of their 

 body. Had the ancient Egyptians been aware of this, their 

 catalogue of insect divinities would have been wofully 

 crowded. In this annular motion, the animal alternately 

 supports each segment of the body upon the plane of position, 

 which it is enabled to do by the little bundles of muscles 

 attached to the skin, that take their origin within the body. 2 



1 Encycl. Brit., art. Physiology, 709. 



2 Cuvier, Anat. Comp. i. 430. 



