Facts and Thotights about Spiders. 187 
(the Ooiichitas, 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 
bprders of the dry ground in readiness to migrate. 
25th. AYent again to visit the spiders, scarcely 
expecting to find them, as, since first seeing them, 
we have had much wdnd and rain. To my surprise 
