ON THE NETS OF GEOMETRIC SPIDERS. 283 
tomology,’ 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 to be intended to 
apply to all), state that the spider always leaves a 
vacant interval round the smallest, first-spun circles 
which are nearest to the centre, but for what pur- 
pose they are unable to conjecture; and that, lastly, 
she bites away the small cotton-like tuft which 
united all the radii at the centre of the net, and in 
the circular opening resulting from this procedure 
she takes her station and watches for her prey. In 
this account I recognize the proceedings of a spider, 
the petra inclinata of Walckenaer, which, as far 
as my own observations extend, never, like the last 
species, converts a radius into a line of communica- 
tion with its retreat; and when it occupies the 
aperture in the centre of its snare, a thread from 
its spinners is generally connected with the inner- 
most circumvolution of the unadhesive spiral line, by 
means of which it quickly lowers itself to the ground 
when suddenly disturbed. But there are other spe- 
cies which rarely, if ever, leave a vacant interval, of 
any considerable magnitude, round that portion of 
the unadhesive spiral line allowed to remain near the 
centre of the net; neither do they form an open- 
ing at the centre, which, almost invariably, is left 
entire. 
The reason why the viscid spiral line is not con- 
