194 LARGE CABBAGE BUTTERFLY. 
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 half 
a foot, or 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 laryee have power to contract the orifice 
of the spinners, so that 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 it 
also 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 cater- 
pillar. In ascending, the animal seizes the thread 
with its jaws, as high as it can reach it; and then, 
elevating that part of the back 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 where it wishes to reach. 
At this time, if taken, it will be found to have a 
packet of thread, from which, however, it soon dis- 
