292 MOTIONS OF INSECTS. 
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 geome- 
ters, have often occasion to descend from branch to 
branch, and sometimes, especially 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! Provi- 
dence, ever watchful over the welfare of the most insig- 
nificant 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 en- 
able them to travel where they please. Shake the 
branches of an oak or other tree in summer, and its in- 
habitants of this description, whether they were reposing, 
moying, or feeding, will immediately cast themselves 
from the leaves on which they were stationed; and how- 
ever sudden your attack, they are nevertheless still pro- 
vided 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 them, 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 mea- 
sure, nor to mark its path that it may find it again; but 
