266 FOOD OF INSECTS. 



Another species, Clubiona atrox, for an account of whose habits we are 

 indebted to Mr. Blackwall, resides in a funnel-shaped silken tube of slight 

 texture, in the corners of windows, or crevices in old walls, &.C., whence 

 it extends lines intersecting each other irregularly at various angles, to 

 which it attaches other lines, or rather fasciculi, of very fine zig-zag threads 

 of a pale blue tint when recent, and of a much more complicated structure 

 than the former, and which adhere strongly to any flies, &:c. coming into 

 contact with them, not from any viscidity, but from their extremely fine 

 filaments attaching themselves to the inequalities in the surface of their 

 prey. These pale-blue fasciculi Mr. Blackwall found to proceed from 

 two additional spinners (or mammulae) peculiar to this species and to three 

 species of Drassus, which are also all four remarkable for having the 

 metatarsal joint of their posterior legs furnished with a very curious comb- 

 ing or rather curling instrument, composed of two parallel rows of curved 

 spines, named by Mr. Blackwall Calamistrum, with which they comb out 

 the peculiar silky material as it issues from these mammulae into that floc- 

 culous texture which gives the pale-blue fasciculi in question their power 

 of retaining the insects that touch them.^ 



You will readily conceive that the geometrical spiders, in forming their 

 concentric circled nets, follow a process very different from that just 

 described, than which, indeed, it is in many respects more curious. As 

 the net is usually fixed in a perpendicular or somewhat oblique direction, 

 in an opening between the leaves of some shrub or plant, it is obvious 

 that round its whole extent will be required lines to which can be attached 

 those ends of the radii that are furthest from the centre. Accordingly the 

 construction of these exterior lines is the spider's first operation. She 

 seems careless about the shape of the area which they enclose, well aware 

 that she can as readily inscribe a circle in a triangle as in a square, 

 and in this respect she is guided by the distance or proximity of 

 the points to which she can attach them.'^ She spares no pains, however, 

 to strengthen and keep them in a proper degree of tension. With the 

 former view she composes each line of five or six or even more threads 

 glued together; and with the latter she fixes to them from different points 

 a numerous and intricate apparatus of smaller threads. Having thus com- 



' Linn. Trans, xvi. 472. and xviii. 223. According to M. Walckenaer's arrangement, 

 the genus Clubiona comes under his division of Errantes. or Wanderers, but certainly C. 

 atrox, which, since my attention was directed to it by Mr. Blackwall's very interesting 

 account of its economy as above, I have very frequently observed in its natural abode and 

 in glasses in which I have kept it, ranges belter under his Sidc.ntairis or Sedentary Spiders, 

 as I have placed it, as I do not believe that it ever stirs from its nest until summoned by the 

 vibrations of its net extended round the opening; and this net, though more irregular in its 

 jitructure, is as truly a net as those of Epcira. I may here mention respecting this species 

 two facts not noticed by Mr. Blackwall, that it has not the power of climbing up a vertical 

 surface of glass ; and that, however old and dusty its main net may be, the pale blue curled 

 or looped fasciculi seem very often renewed, as a pocket-lens rarely fails to detect them in a 

 recent state. 



* It sometitnes happens that the end of the lower line of the triangle in which the geo- 

 metric spiders usually fix their nets, having been attached to a small pebble (or bit of gravel) 

 lying on the ground, this pebble (probably from the spider's tightening its horizontal lines) 

 is drawn up to a considerable height, and swings like a pendulum, as I saw many instances, 

 at first, to my no small surprise, in the Giardino Publico of Milan in 1832 (vide Spence in 

 Loudon's Mao. of Nat. Hint. v. 689.) ; and as has since been observed by W. \V. Saunders, 

 Esq. at Wandsworth. {Trans. Enl. Soc. Lond. \. 127.) In an American newspaper, the 

 Lowell Coxirier was an account of a watchmaker having found one morning a gold ring 

 weighing twelve grains, which he had left on his bench, suspended an inch high to a spider's 

 thread, by which in the course of a week it was elevated eight inches. 



