184 Mr. Black wall on the Construction of the 



ceal herself from observation. From the centre of the net to this retreat 

 she spins a line of communication, composed of several threads united 

 together throughout their entire length, the vibrations of which speedily 

 inform her of the capture of her prey ; and here her labours terminate. 



Such is the process, with some slight modifications now to be noticed, 

 employed by the geometric Spiders in the formation of their snares. One 

 species generally converts a radius into the line of communication between 

 the net and its retreat, instead of spinning a separate line for that pur- 

 pose ; and this peculiar appropriation, whether the radius be in the plane 

 of the snare, or whether it be withdrawn from that plane, as is frequently 

 the case, imparts an unfinished appearance to the net, as it prevents the 

 spider from giving her viscid line a spiral form, though this is sometimes 

 attempted with a greater or less degree of success. No sooner does the 

 Spider arrive at one of the radii adjacent to that in connection with her 

 cell, than she returns, traversing the frame-work of her snare till she 

 arrives at the adjoining radius on the opposite side, when she again re- 

 traces her steps, and thus oscillating between the two, spins a number of 

 curved viscid lines, or arcs of circles, diminishing in length from the 

 circumference of the net towards the centre. Dr. Lister, who has figured 

 and described this species in his Treatise de Araneis, fig. X. p. 47-8, was 

 well acquainted with this peculiaiity so common in the structure of its 

 snare, but he has fallen into the error of supposing that it occurs invari- 

 ably, as appears from the following passage cited from his work. " Rete 

 " amplum & elegantissimum tendit : illud autem in eo perpetuum & sin- 

 " gulare est, nimirum ^ radiis unicum maeulis utrinque nudari, idque d 

 " centro reticuli ad ejus usque circumferentiam ; qui ferfe ad aliquam in 

 " pariete rimulam aut alibi, ubi animal tuto totum diem latet, porrigitur : 

 " atque hie radius ei velut scala est, per quem ascendat descendatque." 



The learned authors of the Introduction to Entomology, in treating 

 upon the construction of the nets of geometric Spiders, (for their remarks, 

 though limited to the proceedings of an individual for the convenience of 

 description, seem intended to apply to all,) state that the Spider always 

 leaves a vacant interval round the smallest first spun circles that are 

 nearest the centre, but for what purpose they are unable to conjecture ; 

 and that lastly, she bites away the small cotton-like tuft that united all the 

 radii at the centre of the net, and in the circular opening resulting from 



