373 
NATURAL-HISTORICAL COLLECTIONS. 
On the Ascent of Spiders in the Air ; communicated to the Institute, in June 
1829, by J.-J. Virey.—It has been long since sought to explain how the Ara-. 
neides attach their webs at extended distances, and cast, so to speak, a bridge of 
cords from one side of a stream to the other, or on the branches of distant plants. 
Some say that the long filaments, left to float on the wind, become agglutinated to 
different bodies, or to other webs, after which the spider gives them a convenient 
tension; and that by means of these threads it transports itself across the interme- 
diate spaces. Lister and other authors have contended, that the animal springs 
to a certain distance, or ejects a glutinous thread, by which it is attached to the 
desired place, from whence it can throw other threads in different directions, and 
then mount or descend at will. 
But there are other observations very embarrassing to explain. Every one has 
remarked in autumn, especially in the earliest frosts, those white webs which cross 
the air at different heights, and which are called by the people gossamer. We 
recognize in them cobwebs whitened probably like hemp-cloth by the prolonged 
action of the air and moisture. These filaments, transported by the winds, raise 
with them little spiders, which they disperse abroad, and which have been exa- 
mined by many German observers, Strach, Buhlmann, Flugg, &c. and especial- 
ly by Gravenhorst, who has described them under the name of Aranea obstetria, 
and of a species of Hpeira less characterized. There are authors who explain 
this transport of the webs of aerial spiders, either by the influence of evaporation, 
or by electricity. John Blackwall has published extended observations on this 
subject.* He shows that these webs, originally formed on the surface of the 
earth, contain the remains of insects, blades of grass, &c. ; but he has not given, 
as we think, a satisfactory explanation of the phenomenon of the aeronautical as- 
cent of these filaments. Bowman -+ has even seen a spider raise itself in the air ; 
but besides the agitation of the wind, of which it could avail itself, he suspected 
that there was some action analogous to attractions or repulsions, capable of sus- 
taining this insect at a height many feet perpendicular above the ground. 
We have, moreover, obtained proof of the spontaneous ascent of little spiders 
especially, (for the larger ones have more difficulty in effecting it,) without any 
web previously existing in the air to sustain them, and without agitation of the 
wind, in a closed chamber. But it is requisite that this fact be supported by 
evidence, and we proceed to detail some experiments repeated with all the care 
which this curious subject deserves, and which any one may perform at pleasure. 
We had often previously observed the ascent of little spiders in the air; but 
presuming that unperceived threads supported them, although we could not con- 
ceive to what object such delicate filaments could adhere, nor how these expert 
rope-dancers could have attached them, we only saw in them the dexterity of 
tumblers. However I was already assured that, to the distance of about two feet, 
a spider could dart a thread towards any point, attach it, and run in a moment 
along the line. They must have ejaculatory tubes in many of their mamil- 
lz, since they eject these threads independent of the others upon which they are 
advancing, and which they are emitting at the same time. 
Further, different kinds of spiders perform sudden leaps, so as not to need the 
support of any thread. But I have not remarked that by means of these leaps 
they are able to rise in the air by describing a parabola like grasshoppers, fleas, 
and other insects whose legs are long. Thus the Lycose, Thomisi, Philodromi, 
and other Citigrade which jump briskly, the Dolomeda, or the Saltigrada, and 
the Phalangita, with long fore feet, make rapid leaps, in every direction, to great 
distances and in the absence of any filament. 
To observe very distinctly the spontaneous ascent of little spiders, it is conve- 
nient to take young individuals of the Epeira diadema, yellow with a black spot, 
* Trans. Linn. Soc. tom. xv. p. 449. + Mag. of Nat. Hist. 1828. 
