182 Mr. Blackwall on the Construction of the 
in places where the insects they prey upon abound. After selecting a 
suitable situation for her purpose, the Spider’s first operation, in most in- 
stances, is to enclose an area, the figure of which appears to be a matter 
of indifference, with lines of her ownspinning. This is effected by pro- 
ceeding along the objects immediately surrounding the space destined to 
be occupied by the net, and attaching to several points, by pressing the 
spinners against them, a line drawn out after her in her transit from one 
to another. These marginal lines she strengthens with a few additional 
ones, and finally gives them the requisite degree of tension by applying 
to them in different directions numerous smaller threads. Having thus 
completed the foundations of her snare, in the next place she commences 
to fill up the outline. Fixing a thread to one of the boundary lines, along 
which she walks, she guides the filament produced in her progress with 
one of her hind feet, that it may not touch in any part and adhere pre- 
maturely; and crossing over to the opposite side, she there attaches it 
firmly by applying her spinners. To the middle of this diagonal thread, 
which is to form the centre of the net, she fixes asecond, which in like 
manner she conveys and fastens to another part of the lines encompass- 
ing the area. Along this last-formed thread she returns, drawing out 
another after her, which, as she does not employ any means to keep it 
distinct, becomes connected with that on which she is advancing, and is 
ultimately glued by its extremity to the centre of the net. In this man- 
ner, but without observing any regularity in the order of her progression, 
she forms about twenty or thirty radii, composed of double lines, diverg- 
ing from the centre to the circumference, and giving the net the appear- 
ance of awheel. She then proceeds to the centre, turns herself round, 
and pulls each radius with her feet to ascertain its strength, breaking such 
as seem defective and replacing them by others. Her next proceeding is 
to produce, round the centre of the net, a spiral line extending thence to 
the circumference, and intersecting the radii, to which she attaches it by 
pressing her spinners against them. This spiral line, a few of the more 
central circumvolutions of which are much nearer to each other than are 
those removed to a greater distance from that point, serves as a temporary 
scaffolding for the Spider to walk over, and also to keep the radii properly 
stretched during her succeeding operations. It, together with the radii 
and marginal lines, is composed of unadhesive silk; but a spiral line has 
