How Animals Work. 



ing on the summit of a post, darted forth four or five 

 threads from its spinners. These, glittering in the 

 sunshine, might be compared to divergent rays of light ; 

 they were not, however, straight, but in undulations 

 little films of silk blown by the wind. They were 

 more than a yard in length, and diverged in an ascend- 

 ing direction from the orifices. The spider then sud- 

 denly 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 deli- 

 cate 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." 



These aerial journeys are undertaken not purely as 

 pleasure trips through the air, but in order to seek 

 fresh hunting grounds where a greater abundance of 

 food may be obtained, and are also the recognized means 

 of dispersal of the family in Spiderland. Large families 

 are the rule rather than the exception among spiders, 

 for the mortality in their infancy is very great ; and if 

 the young spiderkins, which often number several hun- 

 dred, had not this means of dispersal far afield, the 

 majority would perish miserably of starvation, or, as 

 sometimes happens, simply form a cannibalistic feast 



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