344 



FOOD OF INSECTS. 



of it, how is she to know when her prey is entrapped ? For 

 this difficulty our ingenious weaver has provided. She has 

 taken care to spin several threads from the edge of the net 

 to that of her hole, which at once inform her by their vibra- 

 tions 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 inter- 

 secting 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 com- 

 plicated 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 attach- 

 ing themselves to the inequalities in the surface of their 

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

 proceed from two additional spinners (or mammulse) 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 combing 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 mammulse into that flocculous 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 



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

 arrangement, the genus Cluhiona comes under his division of Errantes, or Wan- 

 derers, 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 Sedentaires 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 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 bkie curled or looped fasciculi seem very often re- 

 newed, as a pocket-lens rarely fails to detect them in a recent state. 



