Facts and Thoughts about Spiders, 187 



(the Concliitas, near Buenos Ayres), I noticed a 

 broad white line skirting the low wet ground. This 

 I found was caused by gossamer web lying in such 

 quantities over the earth as almost to hide the grass 

 and thistles under it. The white zone was about 

 twenty yards wide, and outside it only a few 

 scattered webs were visible on the grass ; its exact 

 length I did not ascertain, but followed it for about 

 two miles without finding the end. The spiders 

 were so numerous that they continually baulked 

 one another in their efforts to rise in the air. As 

 soon as one threw out its lines they would become 

 entangled with those of another spider, lanced out 

 at the same moment ; both spiders would imme- 

 diately seem to know the cause of the trouble, for 

 as soon as their lines fouled they would rush 

 angrily towards each other, each trying to -drive 

 the other from the elevation. Notwithstanding 

 these difficulties, numbers were continually floating 

 off on the breeze which blew from the south. 



" I noticed three distinct species : one with a 

 round scarlet body ; another, velvet black, with 

 large square cephalothorax and small pointed abdo- 

 men ; the third and most abundant kind were of 

 different shades of olive green, and varied greatly 

 in size, the largest being fully a quarter of an inch 

 in length. Apparently these spiders- had been 

 driven up from the low ground along the stream 

 where it was wet, and had congregated along the 

 borders of the dry ground in readiness to migrate. 



" 25th. Went again to visit the spiders, scarcely 

 expecting to find them, as, since first seeing them, 

 we have had much wind and rain. To my surprise 



