MOTIONS OF INSECTS. 



273 



noticed them — for at the times when these webs are floating 

 in the air they are very numerous — on the vertical angle of 

 a post or pale, or one of the uprights of a gate, with the end 

 of their abdomen pointing upwards, as if to shoot their 

 thread previously to flying off ; when, upon my approaching 

 to take a nearer view, they have lowered it again, and per- 

 sisted in disappointing my wish to see them mount aloft. 

 The rapidity with which the spider vanishes from the sight 

 upon this occasion, and darts into the air, is a problem of no 

 easy solution. Can the length of web that they dart forth 

 counterpoise the weight of their bodies ; or have they any 

 organ analogous to the natatory vesicles of fishes 1 9 which con- 

 tributes at their will to render them buoyant in the air ? 

 Or do they rapidly ascend their threads in their usual way, 

 and gather them up, till having collected them into a mass of 

 sufficient magnitude, they give themselves to the air, and are 

 carried here and there in these chariots ? I must here give you 

 Mr. White's very curious account of a shower of these webs 

 that he witnessed. On the 21st of September, 1741, intent 

 upon field diversions, he rose before daybreak; but on 

 going out he found the whole face of the country covered 

 with a thick coat of cobweb, drenched with dew, as if two or 

 three setting-nets had been drawn one over the other. When 

 his dogs attempted to hunt, their eyes were so blinded and 

 hoodwinked that they were obliged to lie down and scrape 

 themselves. This appearance was followed by a most lovely 

 day. About nine A. M. a shower of these webs (formed not 

 of single floating threads, but of perfect flakes, some near an 

 inch broad, and five or six long) was observed falling from 

 very elevated regions, which continued without interruption 

 during the whole of the day ; and they fell with a velocity 

 which showed that they were considerably heavier than the 

 atmosphere. When the most elevated station in the country 

 where this was observed was ascended, the webs were still to 

 be seen descending from above, and twinkling like stars in 

 the sun, so as to draw the attention of the most incurious. 

 The flakes of the web on this occasion hung so thick upon 



VOL. II. 



Cuvier, Anat. Comp. i. 504. 

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