MOTIONS OF INSECTS. • 467 



leap ; the strong-made feet and talons of such as dig ; and, to name no 

 more, the admirable faculty of such as cannot fly, to convey themselves 

 with speed and safety, by the help of their webs, or some other artifice, to 

 make their bodies lighter than the air."^ 



Since the motions, and instruments of motion, of insects are usually 

 very different in their preparatory states, from what they are in the 

 imago or perfect state, I shall, therefore, consider them separately, and 

 divide my subject into — motions of larvce, motions of pupse, and motions 

 of perfect insects. 



I. Amongst larva there are two classes of movers ; Apodous larvas, or 

 those that move without legs, and Pedate larvae, or those that move by 

 means of legs. I must here observe, that by the term legs, which I use 

 strictly, I mean only jointed organs, that have free motion, and can walk 

 or step alternately ; not those spurious legs without joints, that have no 

 free motion, and cannot walk or take alternate steps; such as support 

 the middle and anus of the larvfe of most Lepidoptera and saw-flies 

 (^Serrifera) . 



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 honorable ranks in the emble- 

 matical class of their false divinities.^ 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 moi'e deorum, some insects may take their places ; for there are 

 numbers of larvae 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.^ 



> Physico-Theol. Ed. 13. Sns. * Enajcl. Brit., art. Physiology, 709. 



' Cuvier, Anat. Comp. i. 430. 



