On North American Spiders. 117 



were woolly films ; but some of the separate filaments were from 

 forty to fifty feet long. On the 19th of July, 1822, a feu dejoie, 

 fired at Kidderminster, in England, brought down immense numbers 

 of the flying spiders. 



They have the power of darting out their threads to a surpi-ising 

 distance and in any direction ; one of them, by candle light, shot 

 forth a thread of eight feet long to the ceiling of the room, and mak- 

 ing an angle of about 80°, with the horizon. In another instance, 

 during bright sun shine, in a warm day, while the spider was propell- 

 ing threads to all points, it suddenly projected one horizontally, in the 

 direction of the current* from an open door, to the distance of ten 

 feet, and the angle of vision being particularly favorable, an aiii^a or 

 electric atmosphere, as was supposed, was observed about the thread. 



" When swinging from a support, they will soon be perceived to 

 ascend from the perpendicular into the horizontal plane, at each as- 

 cent projecting a thread into the atmosphere ; and at length the in- 

 sect breaks from its anchorage, and ascends. Sometimes aeronautic 

 spiders will take their flight immediately from the surface on which 

 they alight, if the day be warm and sultry : but they generally de- 

 scend to from six to eighteen inches, perhaps the better to insulate 

 themselves, and that, suspended by a pliant thread in free space, they 

 may more freely propel their threads into the atmosphere. Not un- 

 frequently the propulsion of a solitary thread will bear them aloft ; 

 but the air must then be very warm, the sunshine bright, and the 

 electric character of the atmosphere considerable. Sometimes the 

 ascent is so rapid that the eye cannot trace it ; at other times slow 

 and majestic. Occasionally the ascent is quite vertical, and at other 

 times the insect sails on the bosom of the air, either in the horizon- 

 tal plane, or at angles more or less open. It will be also found that 

 there are particular seasons of the year best calculated for this sin- 

 gular exhibition : spring and autumn are these periods. In summer 

 we have found it sometimes impracticable to determine their ascent : 

 they have detached themselves, after several vibrations, and fallen to 

 the ground. On one day, (May, 1823,) this remarkable fact was 

 proved in the case of numbers. The insect seems to be sufficiently 

 aware when the threads are buoyant, and perhaps the temporary sus- 

 pension in the horizontal plane may communicate this information : 

 aeronautic spiders make their appearance early in the season. 



* They sometimes project their threads directly in the teeth of the wind. 



