FOOD OF INSECTS. 231 



from the edge of the net to that of her hole, which at once inform her by 

 their vibrations of the capture of a fly, and serve as a bridge on which in 

 an instant she can run to secure it. 



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 JDrassus, which are also all four remarkable for having the meta- 

 tarsal joint of their posterior legs furnished with a very curious combing or 

 rather curling instrument, composed of two parallel rows of curved spines, 

 named by Mr. Blackwall Calamistrum, with which they comb out the pecu- 

 liar silky material as it issues from these mammulaB into that flocculous 

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

 taining the insects that touch them. 1 



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

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

 scribed, 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. 8 She spares no pains, however, to strengthen 



* Linn. Trans, xvi. 472. and xviii. 223. According to M. Walckenaer's arrange- 

 ment, 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'a 

 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 better under his 

 SGdentaires 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 structure, is as truly a net 

 as those of Epeira. I may here mention respecting this species two facts not no- 

 ticed 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. 



2 It sometimes happens that the end of the lower line of the triangle in which 

 the geometric 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 London's Mag. of Nat. Hist. 

 v. 689.) ; and as has since been observed by W. W. Saunders, Esq. at Wandsworth. 

 (Trans. Ent. Soc. Lond. i. 127.) In an American newspaper, the Lowell Courh*, 



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