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 
ale 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 
rey. These pale-blue fasciculi Mr. Blackwall found to proceed from two 
additional spinners (or mammulz) peculiar to this species and to three 
species of Drassus, 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 mammule into that flocculous 
texture which gives the pale-blue fasciculi in question their power of re- 
taining the insects that touch them. 
You will readily conceive that the geometrical spiders, in forming their 
concentric cireled 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 ina 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 ina 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 
1 Linn, Trans. xvi. 472. and xviii. 223. According to M. Walckenaer’s arrange- 
ment, the genus Clubiona comes under his division of Zrrantes, 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 better under his 
Sédentaires or Sedentary Spiders, as I have placed it, as [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 Hpeira. 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 fascienli 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 Loudon’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 Courier, 
Qt 
