MOTIONS OF INSECTS. 44} 
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.t_ 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 larva, as far as they are known, are not 
yery 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 rostralisy 
will also leap to a considerable height. 
Another species of motion which is peculiar to larva, — their mode I 
mean of climbing,—as it merits particular attention, will occupy more time. 
[have already related so many extraordinary facts in their history, that I 
romise myself you will not disbelieve me if I assert that insects either use 
adders 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 cireamstance, 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 
1 Anat. Comp. i, 430. 2 Rise, I. iv. 112. vi. 14. 
