186 Mr. Blackwall on the Construction of the 
quantity of water completely to immerse their bases, the Spiders, thus 
insulated, use every means in their power to effect an escape; all their 
efforts, however, uniformly prove unavailing in a still atmosphere ; never- 
theless, when exposed to a current of air, or when gently blown upon 
with the breath, they immediately turn the abdomen in the direction of 
the breeze, and emit from the spinning apparatus some of their liquid 
gum, which being carried out ina line by the current, becomes connected 
with some object in the vicinity. This the Spider ascertains by pulling 
at it with her feet, and drawing it in till it is sufficiently tense, she gums 
it fast to the twig, and passing along it speedily regains her liberty. 
Now, that the same means are frequently resorted to by Spiders in their 
natural haunts, for the purposes of changing their situation and fixing the 
foundations of their snares, I have repeatedly observed. 1am aware that 
in the Introduction to Entomology an objection has been urged against 
the explanation of the difficulty here insisted upon. “ If,’’ say the 
learned authors, “‘ the position of the main line be thus determined by — 
“ce 
the accidental influence of the wind, we might expect to see these nets 
arranged with great irregularity, and crossing each other in every direc- 
tion; yet it is the fact, that however closely crowded they may be, 
they constantly appear to be placed not by accident but design, com- 
monly running parallel with each other at right angles with the points 
of support, and never interfering.’”’ In favourable weather, it is well 
known, that the geometric Spiders usually begin to construct their nets 
soon after the close of day, and as similar processes must be influenced 
in a like manner by the simultaneous operation of the same cause, the 
lines of individuals carried out by a current of air till they become at- 
tached to some distant object, will be all parallel or nearly so. This 
regularity, therefore, instead of militating against the opinion maintained 
above, appears to me to furnish a powerful argument in support of it. 
Sometimes the geometric Spiders suspend their nets in places not 
entirely surrounded by objects to which, in the first instance, they can 
proceed and attach their boundary lines. In such cases their operations 
are deserving of attention. After spinning a few radii, which are fixed 
to several distant points most accessible to her, the Spider fastens a thread 
to one of them, gluing it to that extremity which is farthest from the 
centre of her net, Along this radius she walks, drawing out the thread 
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