276 



MOTIONS OF INSECTS. 



the air, as in the instance recorded by Mr. White, is always 

 preceded by gossamer on the ground. Now, since the weather 

 is constantly calm and serene when these showers appear, it 

 cannot be the wind that carries the web from the ground 

 into the air. Again, it is stated that these showers take 

 place after several calm days 1 ; but, if the web was raised by 

 the wind into the air, it would begin to fall as soon as the 

 wind ceased. Whence I am inclined to think that the cause 

 assigned by Dr. Lister is the real source of the whole pheno- 

 menon. Though ordinary observers have overlooked them, 

 he noticed these spiders in the air in such prodigious numbers, 

 that he deemed them sufficient to produce the effect. I shall 

 not, however, decide positively ; but, having stated the dif- 

 ferent opinions, leave you to your own judgment. 



The next query is, What occasions the spiders to mount 

 their chariots and seek the clouds ? Is it in pursuit of their 

 food ? Insects, in the fine warm days in which this pheno- 

 menon occurs, probably take higher flights than usual, and 

 seek the upper regions of the atmosphere ; and that the 

 spiders catch them there, appears by the exuvias of gnats and 

 flies, which are often found in the falling webs. 2 Yet one 

 would suppose that insects would fly high at all times in the 

 summer in serene warm weather. Perhaps the flight of some 

 particular species constituting a favourite food of our little 

 charioteers — the gnats, for instance, which we have seen 

 sometimes rise in clouds into the air — may at these times 

 take place ; or the species of spiders that are most given to 

 these excursions may not abound in their young state — when 

 only they can fly — at other seasons of the year. 



Whether the same species that cover the earth with their 

 webs produce those that fill the air, is to be our next inquiry. 

 Did the appearance of the one always succeed that of the 

 other, this might be reasonably concluded ; but the former, 

 as I lately observed to you, often occurs without being fol- 

 lowed by the latter. Yet, since it should seem that the 

 aerial gossamer, though it does not always follow it, is always 

 preceded by the terrestrial, this warrants a conjecture that 



1 Ray's Letters, 36. 



2 Ibid. 42. Lister, Be Araneis, 8. 



