290 MOTIONS OF INSECTS. 



such an accident, by descending 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 shock. From Iience 

 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, press- 

 ing the silk, can prevent its exit. From hence also it 

 appears that the gummy fluid which forms the thread 

 must have gained a deuree 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 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, 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 found to have a packet of thread, from which, 

 however, it soon disengages itself^ between the two last 

 pairs of perfect legs^. To see hundreds of these little 

 animals pendent at the same time from the boughs of 

 a tree, suspended at different heights, some working 

 their way downwards and some upwards, affords a very 

 amusing spectacle. Sometimes, when the wind is high, 

 they are blown to the distance of several yards from the 

 ti'ee, and yet maintain their threads unbroken. I wit- 

 ■' Reniim. ii. 375 — 



