160 RIO PLATA. [cuap. V1IL. 
was sixty miles distant from the land, in the direction of a steady 
though light breeze. Vast numbers of a small spider, about one- 
tenth of an inch in length, and ofa dusky red colour, were attached 
to the webs. There must have been, I should suppose, some 
thousands on the ship. The little spider, when first coming in 
contact with the rigging, was always seated on a single thread, 
and not on the flocculent mass. This latter seems merely to be 
produced by the entanglement of the single threads. The spiders 
were all of one species, but of both sexes, together with young 
ones. These latter were distinguished by their smaller size and 
more dusky colour. I will not give the description of this spider, 
but merely state that it does not appear to me to be included in 
any of Latreille’s genera. The little a¢ronaut as soon as it arrived 
on board was very active, running about, sometimes letting itself 
fall, and then reascending the same thread ; sometimes employing 
itself in making a small and very irregular mesh in the corners 
between the ropes. It could run with facility on the surface of 
water. When disturbed it lifted up its front legs, in the attitude 
of attention. On its first arrival it appeared very thirsty, and 
with exserted maxille drank eagerly of drops of water; this same 
circumstance has been observed by Strack : may it not be in con- 
sequence of the little insect having passed through a dry and rare- 
fied atmosphere? Its stock of web seemed inexhaustible. While 
watching some that were suspended by a single thread, I several 
times observed that the slightest breath of air bore them away 
out of sight, in a horizontal line. On another occasion (25th) 
under similar circumstances, I repeatedly observed the same kind 
of small spider, either when placed or having crawled on some 
little eminence, elevate its abdomen, send forth a thread, and then 
sail away horizontally, but with a rapidity which was quite un- 
accountable. I thought I could perceive that the spider, before 
performing the above preparatory steps, connected its legs toge- 
ther with the most delicate threads, but I am not sure whether 
this observation was correct. 
One day, at St. Fé, I had a better opportunity of observing 
some similar facts. A spider which was about three-tenths of 
an inch in length, and which in its general appearance resembled 
a Citigrade (therefore quite different from the gossamer), while 
standing on the summit of a post, darted forth four or five threads 
