J74 CHARLES DARWIN 



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 aeronaut 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 the water. When 

 disturbed it lifted up its front legs, in the attitude of atten- 

 tion. On its first arrival it appeared very thirsty, and with 

 exserted maxillae drank eagerly of drops of water ; this same 

 circumstance has been observed by Strack: may it not be in 

 consequence of the little insect having passed through a dry 

 and rarefied atmosphere? Its stock of web seemed inex- 

 haustible. 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 emi- 

 nence, elevate its abdomen, send forth a thread, and then 

 sail away horizontally, but with a rapidity which was quite 

 unaccountable. I thought I could perceive that the spider, 

 before performing the above preparatory steps, connected 

 its legs together with the most delicate threads, but I am not 

 sure whether this observation was correct. 



One day, at St. Fe, 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 from its spinners. These, glitter- 

 ing in the sunshine, might be compared to diverging rays of 

 light; they were not, however, straight, but in undulations 

 like films of silk blown by the wind. They were more than a 

 yard in length, and diverged in an ascending direction from 

 the orifices. The spider then suddenly let go its hold of the 

 post, and was quickly borne out of sight. The day was hot 

 and apparently calm; yet under such circumstances, the at- 



