544 PHILOSOPHICAL TRANSACTIONS. [aNNO 17 10. 



end of each leg, and a spongy substance between them, which is doubtless of 

 service to them when they go upon smooth bodies. 



The hinder part of the body of this insect is joined to the fore part only by 

 a small thread, and covered with a thin skin, on which are hairs of divers co- 

 lours; it contains the back, belly, parts of generation, and the anus. It is 

 certain, that all spiders spin their threads from the anus, about which there are 

 five papillae, or small nipples, which at first sight one would take for so many 

 spindles, that serve to form the thread ; I have found these papillae to be mus- 

 cular, and furnished with a sphincter. A little within these I have observed two 

 others, from the middle of which issue several threads, in a pretty large quan- 

 tity, sometimes more, and sometimes less, which the spiders make use of after 

 a very mechanical manner, when they want to go from one place to another ; 

 they hang themselves perpendicular by a thread, and turning their head towards 

 the wind, they shoot several others from their anus, like so many darts ; and if 

 by chance the wind, which spreads them abroad, fastens them to any solid 

 body, which they perceive by the resistance they find in drawing them in from 

 time to time with their feet, they then make use of this kind of bridge, to pass 

 to the place where their threads are fixed. But if these threads meet with no- 

 thing to fix on, the spiders continue to let them out further, till their great 

 length, and the force with which the wind drives them, surpassing the weight 

 of their bodies, they find themselves to be strongly drawn ; and then breaking 

 the first thread, which they hung by, they let themselves loose to be driven by 

 the wind, and flutter on their backs in the air with their legs stretched out. 

 And by these two ways it is, that they pass over roads, streets, and the broadest 

 rivers. See fig. 18 and 19, pi. 12. 



One may himself wind up these threads, which by reason of their being 

 united together, seem to be but one when they are about a foot in length ; 

 but I have distinguished them into 15 or 20 at their issuing from the anus. 

 What is further remarkable, is the ease with which this insect moves its anus 

 every way, by means of the many rings that border upon it. This is absolutely 

 necessary for them, in order to wind up their threads or silk, which in the fe- 

 male spider is of two sorts. However, I believe this insect to be androgynous, 

 or hermaphrodite, having always found the signs of a male in such spiders as 

 lay eggs. The first thread that they wind is weak, and serves them for no 

 other use than to make that sort of web, in which they catch flies. The second 

 is much stronger : in this they wrap up their eggs, and by this means preserve 

 them from the cold, and secure them from such insects as would destroy them. 

 These last threads are wrapped very loosely about their eggs, and resemble in 

 form the bags of silk-worms, that have been prepared and loosened between 



