Silk Spider (Nephila Plumipes Koch), a geometric spider of the family epeiridoe, first brought to notice by Dr. B. G. Wilder in 1865; he discovered it on the sea islands off the coast of South Carolina. The female is 1.1 in. long, with a longitudinal spread of legs 2¾ in., and a lateral extent of 3¾- in.; the cephalo-thorax is black above, mostly covered with silvery hairs; abdomen olive brown, with yellow and white spots and stripes; eye spots black and eight in number; it received its specific name from the closely set stiff brushes of hairs on the legs. They are found in forests, building strong viscid webs, 3 to 4 ft. in diameter, and usually over 10 ft. from the ground. The web is made of a dry, inelastic, silvery gray silk, and of a very elastic, viscid yellow silk; the former is the supporting radiating framework, and the latter forms the concentric entangling circles. It sucks out the gum of its old web for making a new one; this is a circle minus its upper sextant, consisting of a continuous spiral viscid line laid upon the numerous radii. The spider remains quiet in its web, head downward, and is very active upon it when a fly is entangled; it is slow on the ground, and likes the full glare of the sun.

The web is never vertical, but inclined at an angle of 70°; when it is touched, it shakes its web violentlv. Like most if not all geometric spiders, though well provided with eyes, it can distinguish only light; if the insect caught happens to be on a radius beyond her reach, she cannot see it, and returns to the centre to shake the web and ascertain what radius holds the weight; two spiders will often approach each other till their legs interlock before they are aware of their proximity. Hearing and touch are acute. The males are only a quarter of an inch long, with the legs spreading laterally and longitudinally about three fourths of an inch; the body and legs are dark brown; they make no webs, unless when very young, and seem to hang on to that of some female, or to some part of her body. Prof. Wilder had an idea that the silk of this spider might be useful in the arts, and devised several ingenious ways to procure it. He found that from one pair of spinners came white and from another yellow silk, which he was enabled to wind separately by a simple machine to the extent of nearly two miles, at 170 revolutions a minute, in less than five hours of winding time; he could not reel more than 300 yards at one time; the diameter varied from 1/6000 to 1/000 of an inch, and its strength was very great.

For details see the "Popular Science Monthly" for April, 1875.