MOTIONS OF INSECTS. 



277 



they may be synonymous. Two German authors, Bechstein 1 

 and Strack 2 , 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. ohtextrix as 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 Lister observed as 

 remarkable for taking aerial flights 3 , 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. 4 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." 5 The 

 more expanded the web the lighter and more buoyant, and 

 the more condensed the heavier it must be. 



I trust you will allow, from this mass of evidence, that the 

 English Arachnologists — may I coin this term ? — were 

 correct in their account of this singular phenomenon; and 

 think, with me, that Swammerdam (who, however, admits that 

 spiders sail on their webs), and after him De Geer, were 

 rather hasty when they stigmatised the discovery that these 

 animals shoot their webs into the air, and so take flight, as a 



i Lichtenberg und Voight Magazin, 1789, vi. 53. 



■2 Neue Schriften der Naturforsch. &c. 1810, v. Heft. 41 — 56. 



1 De Araneis, 66. 4 Ibid. 79. 5 Nat. Hist. i. 326, 



T 3 



