MOTIONS OF INSECTS. 503 



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 different opinions, leave you to your ovv'n 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 ihe exuviae 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. Per- 

 haps the flight of some particular species constituting a favorite food of 

 our little charioteers — the gnats, for instance, which we have seen some- 

 times 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 con- 

 cluded ; 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 Aranea ohtextrix. 

 But it is not clear, unless they have described it at different ages, when 

 spiders often greatly change their appearance, that they mean the same 

 species. The former describes his as of the size of a small pin's head, 

 with its eight eyes disposed in a circle, having a black brown body and 

 light yellow legs: while Dr. Strack represents his A. obtextrix a.s more 

 than two lines in length ; eyes four in a square, and two on each side 

 touching each other ; thorax deep brown, with paler streaks ; abdomen 

 below dull white, above dark copper brown, with a dentated white spot 

 running longitudinally down the middle. The first of these, if distinct, 

 as I suspect they are, agrees very well with the young of one which Lis- 

 ter observed as remarkable for taking aerial flights^, and which I have 

 most usually seen so engaged. The other may possibly be that before 

 noticed, which he found in such infinite numbers in Cambridgeshire.^ If 

 this conjecture be correct, it will prove that the same species first produce 

 the gossamer that covers the ground, and then, shooting other threads, 

 mount upon them into the air. 



My last query was. What causes these webs ultimately to fall to the 

 earth ? Mr. White's observation will, I think, furnish the best answer. 

 " If the spiders have the power of coiling up their webs in the air, as Dr. 

 Lister affirms, then when they become heavier than the air they will fall."^ 

 The more expanded the web the lighter and more buoyant, and the more 

 condensed the heavier it must be. 



' Ibid. 42. Lister, De Araneis, 8. 



* Lichtejiberg und Vuishf. Mas^azin, 1789, vi. 53. 



» Ntiie Sr.hriften der Natur/or'sck. &c. 18 10, v. Hefl. 41—56. 



* De Araneis, 66. * Ibid. 79. « Nat. Hist. i. 326. 



