346 INSECT ARCHITECTURE. 



a stick of excited sealing-wax is brought near the 

 thread of suspension, it is evidently repelled ; con- 

 sequently, the electricity of the thread is of a nega- 

 tive character," while " an excited glass tube brought 

 near seemed to attract the thread, and with it the 

 aeronautic spider."* His friend Mr. Bowman fur- 

 ther describes the aerial spider as "shooting out 

 four or five, often six or eight, extremely fine webs 

 several yards long, which waved in the breeze, di- 

 verging from each other like a pencil of rays." One 

 of them " had two distinct and widely diverging fasi- 

 culi of webs," and " a line uniting them would have 

 been at right angles to the direction of the breeze."t 



Such is the chief evidence in support of the elec- 

 trical theory ; but though we have tried these ex- 

 periments, we have not succeeded in verifying any 

 one of them. The following statements of Mr. Black- 

 wall come nearer our own observations. 



5. "Having procured a small branched twig," says 

 Mr. Blackwall, " I fixed it upright in an earthen ves- 

 sel containing water, its base being immersed in the 

 liquid, and upon it I placed several of the spiders 

 which produce gossamer. Whenever the insects 

 thus circumstanced were exposed to a current of air, 

 either naturally or artificially produced, they directly 

 turned the thorax towards the quarter whence it 

 came, even when it was so slight as scarcely to be 

 perceptible, and, elevating the abdomen, they emitted 

 from their spinners a small portion of glutinous 

 matter, which was instantly carried out in a line, 

 consisting of four finer ones, with a velocity equal, 

 or nearly so, to that with which the air moved, as 

 was apparent from observations made on the motion 

 of detached lines similarly exposed. The spiders, 

 in the next place, carefully ascertained whether their 



* Experim. Researches in Nat. Hist. p. 136. 

 f Mag. Nat. Hist., vol. i. p. 324. 



