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MR. BLACKW ALL'S RESEARCHES RESPECTING SPIDERS *. 



It may be known to most of our readers, that Mr. Black wall was the 

 first to discover the mode in which the line of a spider can be thrown 

 across brooks and other places inaccessible to the animal, — a subject 

 upon which a great deal of error had been propagated, even by natural- 

 ists of high name. His experiments were extensively repeated and 

 confirmed, as has been recorded in Insect Architecture, upon this point ; 

 and we have now to mention other researches of the same ingenious 

 character respecting the economy of spiders. His remarks were 

 chiefly made on Clubiona atrox, a very common species, whose web 

 must have caught the attention of all who attend to these interesting 

 animals. 



" The favourite haunts," says Mr. Blackwall, " of Clubiona atrox are the 

 branches of trees and shrubs growing against buildings, crevices in old walls, and 

 the corners of windows. In these and similar localities it fixes its residence and 

 fabricates its snare. On the objects surrounding the spot selected for its retreat, it 

 extends to a considerable distance, but without any apparent regularity of design, a 

 number of fine shining lines intersecting each other at various angles, to which it 

 attaches other lines, or rather fasciculi of threads of a more complicated structure, 

 and of a pale blue tint, nearly approaching the colour of skimmed milk. These com- 

 pound threads, or flocculi, which, in exposed situations, retain their delicate hue for 

 a short period only, (old webs being generally of a dull or sullied white, not at all 

 advantageous to their appearance,) are arranged on the first spun glossy lines, both 

 in longitudinal and transverse directions. When recently produced, they adhere 

 strongly to such insects as come in contact with them, and, though perfectly ine- 

 lastic, may be drawn out into fibres of extreme tenuity. The communication between 

 the snare of this spider and its retreat, is established by means of a funnel-shaped 

 tube of a slight texture, whose smaller extremity is in immediate connection with the 

 latter, and, indeed, sometimes constitutes the animal's abode. Not unfrequently 

 two or more tubes occur in the same web, by one or other of which the spider 

 usually effects its retreat when disturbed. 



" If a new-formed flocculus be minutely examined under the microscope, with a 

 pretty high magnifying power, it will be found to consist of six lines. Two of 

 these filaments are straight and exceedingly attenuated ; and upon each of them is 

 disposed a tortuous white line inflected into short curves and loops, like a ravelled 

 thread of fine silk. A pale blue band, thickly distributed on each of the inflected 

 lines in numerous irregular curvatures, completes the flocculus. The flexures of the 

 pale blue bands are more widely extended than those of the white tortuous lines on 



* Notice of several recent Discoveries in the Structure and Economy of Spiders. 

 By John Blackwall, Esq., F.L.S. Linn. Trans, vol. xvi. 



