468 MOTIONS OF INSECTS. 



observant friend, thinking the numbers of the flying spiders not sufficient 

 to produce the whole of the phenomenon in question, is of opinion that an 

 equinoctial gale, sweeping along the fallows and stubbles coated with the 

 gossamer, must bring many single threads into contact, which, adhering to- 

 gether, may gradually collect into flakes ; and that being at length detached 

 by the violence of the wind, they are carried along with it : and as it is 

 known that such winds often convey even sand and earth to great heights, 

 he deems it highly probable that so light a substance maybe transported to 

 so great an elevation as not to fall to the earth for some days after, when 

 the weather has become serene, or to descend upon ships at sea, as has 

 sometimes happened. This, which is in part adopted from the German 

 authors, is certainly a much more reasonable supposition than the other; 

 but some facts seem to militate against it : for, in the first place, though 

 gossamer often occurs upon the ground when there is none in the air, yet 

 the reverse of this has never been observed ; for gossamer in 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 tliese showers take j)lace after 

 several calm days^; 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 

 phenomenon. Though ordinary observers have overlooked them, he no- 

 ticed these spiders in the air in such prodigious numbers, that he deemed 

 them sufficient to produce the effect. I shall not, however, decide posi- 

 tively ; but, having stated the different 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 phenomenon 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.** 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 

 followed 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 they may be synonymous. Two German 

 authors, Bechstein^ and Strack*, have described the spider that produces 

 gossamer in Germany under the name of Arnnea obtextrix. But it is not 



1 Ray's Letters, 36. 2 i^id. 42. Lister, De Araneis, 8. 



3 Lichtenberg und Voialit Magazin, 1789, vi. 53. 



<» Neue Schriften der Naturforsch. &c. IblO, v. Heft. 41—56. 



