On North American Spiders. 137 
were woolly films; but some of the separate filaments were from 
forty to fifty feet long. On the 19th of July, 1822, a few de joie, 
fired at Kidderminster, in England, brought down immense numbers 
of the flying spiders. 
They have the power of darting out their threads to a surprising 
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 aura 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 aéronautic 
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 ; 
ut 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 
limes the insect sails on the bosom of the air, either in the horizon- 
tal plane, or at angles more or lesopen. 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 
° stound. 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 : 
*tonautic spiders make their appearance early in the season. 
BD arene EN 
: . 
my Sometimes project their threads directly in the teeth of the wind. 
