MOTIONS OF INSECTS. 293 
thus, whenever the caterpillar falls or would descend 
from a leaf, it has a cord always ready to support it in 
the air, by lengthening which it can with ease reach the 
ground, Thus it can drop itself without danger from 
the summit of the most lofty trees, and ascend again by 
the same road. As the silky matter is fluid when it 
issues from the spinners, it should seem as if the weight 
of the insect would be too great, and its descent too 
rapid, so as to cause it to fall with violence upon the 
earth. ‘The little animal knows how to prevent such an 
accident, by descending gradually. It drops itself a foot 
or halfa foot, or even less, at a time; then making a 
longer or shorter pause, as best suits it, it reaches the 
ground at last without a shock. From hence it appears 
that these larvae have power to contract the orifice of 
the spinners, so as that no more of the silky gum shall 
issue from it; and to relax it again when they intend to 
resume their motion downwards: consequently there 
must be a muscular apparatus to enable them to effect 
this, or at least a kind of sphincter, which, pressing the 
silk, can prevent its exit. From hence also it appears, 
that the gummy fluid which forms the thread must have 
gained a degree of consistence even before it leaves the 
spinner, since as soon as it emerges it can support the 
weight of the caterpillar—In ascending, the animal 
seizes the thread with its jaws as high as it can reach it; 
and then elevating that part of the baci that corresponds 
with the six perfect legs, till these legs become higher 
than the head, with one of the last pair it catches the 
thread; from this the other receives it, and so a step Is 
gained: and thus it proceeds till it has ascended to the 
point it wishes to reach. At this time if taken it will be 
