456 SUPPLEMENT 



according to the same author, has accorded to each spider a 

 sufficient quantity of the silky matter to make six or seven 

 webs during its life. When no more remains, they must either 

 die, or appropriate to themselves the production of others. 



The life of many species scarcely extends beyond the terra 

 of eight or twelve months. But the mygales, the spiders 

 properly so called, and the lycosas, can live many years. 

 Many pass the winter shut up in holes concealed under 

 stones. Some even construct for themselves, in that season, a 

 cocoon of silk, which serves them as a retreat. 



In the fine days in autumn, we may see floating in the air 

 a tolerable quantity of threads of silk, which are often carried 

 by the wind to a considerable height. Many of these threads 

 are the work of some young araneides ; of this we may convince 

 ourselves by examining them closel}'. We shall find at one of 

 the ends, little spiders occupied in producing new threads, 

 or elongating those which have been already spun, until they 

 are fixed at a distance to some solid place, whither they can 

 transport themselves. 



Quatremee d'Isjonval believed that he discovered in the 

 epeirae, a natural barometer ; but it does not appear that this 

 opinion has been followed up, or has led to any results. 



The spiders of the genus Mygale appear to be nocturnal 

 animals. Their sombre colours, and some observations which 

 have been made upon them, seem to authorize this conjecture. 

 They establish their domicile in cavities usually subterraneous, 

 Avhich they either prepare for themselves or find by chance, 

 and whose aperture they line after the manner of the tubicolae, 

 which are likewise nocturnal animals. 



In this genus are found those monstrous araneides which 

 can occupy a circular space of from seven to eight inches in 

 diameter, and which sometimes even seize small birds. 



These species are in general peculiar to the equatorial 

 countries, and those wliich border on the tropics. They are 



