Il6 AERONAUT SPIDERS. [CHAP, via 



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 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 circum- 

 stances, 1 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 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, 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, glittering 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 quite calm ; yet under such circumstances, 

 the atmosphere can never be so tranquil as not to affect a vane so 

 delicate as the thread of a spider's web. If during a warm day we 

 look either at the shadow of any object cast on a bank, or over a level 

 plain at a distant landmark, the effect of an ascending current of 

 heated air is almost always evident : such upward currents, it has 

 been remarked, are also shown by the ascent of soap-bubbles, which 

 will not rise in an indoors room. Hence I think there is not much 

 difficulty in understanding the ascent of the fine lines projected from 

 a spider's spinners, and afterwards of the spider itself; the divergence 

 of the lines has been attempted to be explained, I believe by 

 Mr. Murray, by their similar electrical condition. The circumstance 

 of spiders of the same species, but of different sexes and ages, being 

 found on several occasions at the distance of many leagues from the 

 land, attached in vast numbers to the lines, renders it probable that 

 the habit of sailing through the air is as characteristic of this tribe, 

 as that of diving is of the Argyroneta. We may then reject Latreille's 

 supposition, that the gossamer owes its origin indifferently to the 

 young of several genera of spiders : although, as we have seen, the 

 young of other spiders do possess the power of performing aerial 

 voyages.* 



During our different passages south of the Plata, I often towed 

 astern a net made of bunting, and thus caught many curious animals. 

 Of Crustacea there were many strange and undescribed genera. One, 



* Mr. Blackwall, in his "Researches in Zoology," has many excellent 

 observations on the habits of spiders, 



