MOTIONS OF INSECTS. i 345 



with its eight eyes disposed in a circle, having a black- 

 brown body and light-yellow legs : while Dr. Strack 

 represents his A. obiexlrix as more than two lines in 

 length ; eyes lour in a square, and two on each side 

 touching each other ; thorax deep brown with paler 

 streaks; abdoaien below dull white, above dark cop- 

 per brown, with a dentated white soot running longi- 

 tudinally down the middle. The first of these, if di- 

 stinct, as I suspect they are, agrees very well witii the 

 young of one which Lister observed as remarkable for 

 taking aerial ilights^; and which I have most usually 

 seen so engaged. The other may possibly be that be- 

 fore noticed, v/liich lie found in such infinite numbers 

 in Cambridgeshire''. If this conjecture be correct, it 

 will prove that the same species first produce the gos- 

 samer that covers the ground, and then, shooting other 

 threads, mount upon them into the air. 



My last query was, What causes these webs at last 

 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 afhrms, 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. 



I trust you will allow from this mass of evidence, 

 that the English AracJinologisls — may I coin this term ? 

 — were correct in their account of this singular phe- 

 nomenon ; and think, with me, that Swanimerdam (who 

 hov/ever admits that spiders sail on their webs), and 

 after him De Geer, were rather hasty when they stig- 



^ De Jraneis, 66. " Ibitl. 79. ' Nal. Hist, i. 3§6. 



