374 Insect Architecture. 



threads from the nipples, which, being lengthened out and 

 driven by the wind to some neighbouring tree or other 

 object, are by their natural clamminess fixed to it."* 



Observation gives some plausibility to the latter opinion, 

 as the spider always actively uses her legs, though not to 

 draw out the thread, but to ascertain whether it has caught 

 upon any object. The notion of her pressing the spinneret 

 with her feet must be a mere fancy ; at least it is not coun- 

 tenanced by anything which we have observed. 



4. An opinion much more recondite is mentioned, if it 

 was not started, by M. D'Isjonval, that the floating of the 

 spider's thread is electrical. "Frogs, cats, and other 

 animals," he says, " are affected by natural electricity, and 

 feel the change of weather ; but no other animal more than 

 myself and my spiders." During wet and windy weather 

 he accordingly found that they spun very short lines, " but 

 when a spider spins a long thread, there is a certainty of 

 fine weather for at least ten or twelve days afterwards. "j A 

 periodical writer, who signs himself Carolan,J fancies that in 

 darting out her thread the spider emits a stream of air, or 

 some subtle electric fluid, by which she guides it as if by 

 magic. 



A living writer (Mr. John Murray), whose learning and 

 skill in conducting experiments give no little weight to his 

 opinions, has carried these views considerably farther. 

 " The aeronautic spider," he says, " can propel its thread 

 both horizontally and vertically, and at all relative angles, 

 in motionless air, and in an atmosphere agitated by winds ; 

 nay more, the aerial traveller can even dart its thread, to 

 use a nautical phrase, in the 'wind's eye.' My opinion 

 and observations are based on many hundred experiments. 

 .... The entire phenomena are electrical. When a 

 thread is propelled in a vertical plane, it remains perpendi- 

 cular to the horizontal plane, always upright, and when 

 others are projected at angles more or less inclined, their 



* Animal Biography, vol. iii. p. 475, 3rd edition, 

 t Brez, Flore des Insect ophiles. Notes, Supp. p. 134. 

 + Thomson's Ann. of Philosophy, vol. iii. p. 306. 



