^ MOTIONS OF INSECTS. 293 



find it again : but thus, whenever the caterpillar falls 

 or would descend from a leaf, it has a cord always 

 ready to support it in the air, l)y 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 wlien 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 ani- 

 mal knows how to prevent such an accident, by de- 

 scending gradually. It drops itself a foot or half a 

 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 sliock. From hence it appears that 

 these larvai have power to contract tlie orifice of the 

 spinners, so as that no more of the silky gum shall is- 

 sue from it ; and to relax it again when they intend to 

 resume their motion downwards : consequently there 

 must be a muscu'ar apparatus to enable them to effect 

 this, or at least a kind of sphincter, vvhich, 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 bc(bre it leaves 

 the spinner, since as soon as it emerges it can support 

 the weight of the caterpillar. — In ascending, the ani- 

 mal 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 be- 

 come higher than the head, with one of the last pair it 

 catches the thread ; from this the other receives it, anif 

 so a step is gained : and thus it proceeds till it has 



