MOTIONS OF INSECTS. 441 



themselves along, in the same manner as a chimney-sweeper by the 

 pressure of his knees, elbows, shoulder-blades, and other prominent parts 

 pushes himself up a chimney. 1 The larva of the ant-lion (Myrmelion), 

 with the exception of one species, which moves in the common way, always 

 walks backwards, even when its legs are cut off. 



The jumpers, amongst pedate larvae, as far as they are known, are not 

 very numerous, and will not detain you long. When the caterpillar of 

 Lithosia Quadra, a moth not uncommon, would descend from one branch or 

 leap to another, it approaches to the edge of the leaf on which it is sta- 

 tioned, bends its body together, and retiring a little backwards, as if to 

 take a good situation, leaps through the air, and, however high the jump, 

 alights on its legs like a cat. That of another moth (Herminia rostralis) 

 will also leap to a considerable height. 2 



Another species of motion which is peculiar to larvae, their mode I 

 mean of climbing, as it merits particular attention, will occupy more time. 

 I have already related so many extraordinary facts in their history, that I 

 promise myself you will not disbelieve me if I assert that insects either use 

 ladders for this purpose, or a single rope. You may often have seen the 

 caterpillar of the common cabbage-butterfly climbing up the walls of your 

 house, and even over the glass of your windows. When next you witness 

 this last circumstance, if you observe closely the square upon which the 

 animal is travelling, you will find that, like a snail, it leaves a visible track 

 behind it. Examine this with your microscope, and you will see that it 

 consists of little silken threads, which it has spun in a zigzag direction, 

 forming a rope-ladder, by which it ascends a surface it could not otherwise 

 adhere to. The silk as it comes from the spinners is a gummy fluid, which 

 hardens in the air ; so that it has no difficulty in making it stick to the 

 glass. Many caterpillars that feed upon trees, particularly the geometers, 

 have often occasion to descend from branch to branch, and sometimes, es- 

 pecially previously to assuming the pupa, to the ground. Had they to 

 descend by the trunk, supposing them able to traverse with ease its rugged 

 bark, what a circuitous route must they take before they could accomplish 

 their purpose ! Providence, ever watchful over the welfare of the most 

 insignificant of its creatures, has gifted them with the means of attaining 

 these ends, without all this labour and loss of time. From their own 

 internal stores they can let down a rope, and prolong it indefinitely, which 

 will enable them to travel where they please. Shake the branches of an 

 oak or other tree in summer, and its inhabitants of this description, whether 

 they were reposing, moving, or feeding, will immediately cast themselves 

 from the leaves on which they were stationed ; and however sudden your 

 attack, they are nevertheless still provided for it, and will all descend by 

 means of the silken cord just alluded to, and hang suspended in the air. 

 Their name of geometer was given to a large division of the caterpillars 

 which have this power of descending by silken threads, because they seem 

 to measure the surface they pass over, as they walk, with a chain. If you 

 place one upon your hand, you will find that they draw a thread as they 

 go ; when they move, their head is extended as far as they can reach with 

 it ; then fastening their thread there, and bringing up the rest of their body, 

 they take another step ; never moving without leaving this clue behind 

 them ; the object of which, however, is neither to measure, nor to mark its 



i Anat. Comp. i. 430. 2 Rosel, T. iv. 112. vi. 14. 



