STRUCTURE, FUNCTIONS AND tECONOMY OF ARANEIDEA. 77 



domicile the female spins several globular cocoons of yellowish-white silk of 

 a slight texture, whose mean diameter is about one-eighth of an inch, in each 

 of which she deposits from twenty to sixty small spherical eggs of a pale 

 yellowish-white colour, not agglutinated together. The young remain with 

 the mother for a long period after quitting the cocoons, and are provided by 

 her with food, which consists chiefly of ants*. 



Oonops pulcher constructs several contiguous, subglobose cocoons of white 

 silk of a iine but compact texture in the crevices of rocks and walls, and 

 among lichens growing on the trunks of trees ; each measures about one- 

 sixteenth of an inch in diameter and usually comprises two spherical, pink 

 eggs, not agglutinated together. It may be remarked, by way of contrast, that 

 Ep'eira quadrata frequently deposits between nine hundred and a thousand 

 spherical eggs of a yellow colour, in a globular cocoon of coarse yellow silk 

 of a loose texture, measuring seven-tenths of an inch in diameter, which is 

 attached to the stems of heath, gorse, and other vegetable productions in the 

 vicinity of its haunts. 



Among the silken snares fabricated by spiders for the purpose of capturing 

 their prey, the most elegant are those constructed with the appearance of 

 geometrical precision in the form of circular nets. They are composed of an 

 elastic spiral line thickly studded with minute globules of liquid gum, whose 

 circumvolutions, falling within the same plane, are crossed by radii conver- 

 ging towards a common centre, which is immediately surrounded by several 

 circumvolutions of a short spiral line devoid of viscid globules, forming a 

 station from which the toils may be superintended by their owner without 

 the inconvenience of being entangled in them. As the radii are unadhesive 

 and possess only a moderate share of elasticity, they must consist of a d liferent 

 material from that of the viscid spiral line, which is elastic in an extraordinary 

 degree. Now the viscidity of this line may be shown to depend entirely upon 

 the globules with which it is studded, for if they be removed by careful ap- 

 plications of the finger, a fine glossy filament remains, which is highly elastic, 

 but perfectly unadhesive. As the globules, therefore, and the line on which 

 they are disposed, differ so essentially from each other, and from the radii, it is 

 reasonable to infer that the physical constitution of these several portions of 

 the net must be dissimilar. 



An estimate of the number of viscid globules distributed on the elastic 

 spiral line in a net of Epiiira apoclisa of a medium size, will convey some 

 idea of the elaborate operations performed by the Epeirce in the construction 

 of their snares. The mean distance between two adjacent radii, in a net of 

 this species, is about seven-tenths of an inch ; if, therefore, the number 7 be 

 multiplied by 20, the mean number of viscid globules which occur on one- 

 tenth of an inch of the elastic spiral line, at the ordinary degree of tension, 

 the product will be 140, the mean number of globules deposited on seven- 

 tenths of an inch of the elastic spiral line ; this product multiplied by 24, the 

 mean number of circumvolutions described by the elastic spiral line, gives 

 3360, the mean number of globules contained between two radii ; which 

 multiplied by 26, the mean number of radii, produces 87,360, the total 

 number of viscid globules in a finished net of average dimensions. A large 

 net, fourteen or sixteen inches in diameter, will be found, by a similar calcu- 

 lation, to contain upwards of 120,000 viscid globules, and yet Epeira 

 apoclisa will complete its snare in about forty minutes if it meet with no in- 

 terruption. 



In the formation of their snares the Epeirce appear to be regulated solely 

 by the sense of touch, as various species when confined in spacious glass jars 

 * Researches in Zoology, p. 356. 



