Page:The history of silk, cotton, linen, wool, and other fibrous substances 2.djvu/186

 ''*most perpendicular, they emitted from their spinning apparatus a small quantity of the glutinous secretion with which they construct their webs''. This viscous substance being drawn out by the ascending current of rarefied air into fine lines several feet in length, was carried upward, until the spiders, feeling themselves acted upon with sufficient force in that direction, quitted their hold of the objects on which they stood, and commenced their journey by mounting aloft.

"Whenever the lines became inadequate to the purpose for which they were intended, by adhering to any fixed body, they were immediately detached from the spinners and so converted into terrestrial gossamer, by means of the last pair of legs, and the proceedings just described were repeated; which plainly proves that these operations result from a strong desire felt by the insects to effect an ascent ." Mr. Blackwall has recently read a paper (still unpublished) in the Linnæan Society, confirmatory of his opinions.

6. "Without going into the particulars," says Mr. Rennie, "of what agrees or disagrees in the above experiments with our own observations, we shall give a brief account of what we have actually seen in our researches. So far as we have determined, then, all the various species of spiders, how different soever the form of their webs may be, proceed in the circumstance of shooting their lines precisely alike; but those which we have found the most manageable in experimenting, are the small gossamer spider (Aranea obtextrix, ), known by its shining blackish-brown body and reddish-brown semi-transparent legs; but particularly the long-bodied spider (Tetragnatha extensa, ), which varies in color from green to brownish or grey—but has always a black line along the belly, with a silvery white or yellowish one on each side. The latter is chiefly recommended by being a very industrious and persevering spinner, while its movements are easily seen, from the long cylindrical form of its body and the length of its legs.

"We placed the above two species with five or six others, including the garden, the domestic, and the labyrinthic spiders,