ae eee ae ee!) le ee ee ee. ae pin . = = 7 ~ | 
CONSTRUCTION OF AN ORBWEB. 61 
Dr. Hulse, as early as A. D. 1670, noticed the habits of spiders to make ~ 
various anchorages of their drag line as they moved along. He thus wrote 
to Mr. Ray: “ They will often fasten their threads in several places to the 
things they creep up: the manner is by beating their bums or tails against 
them as they creep along. This line will express the way :— 
By this frequent beating in of their thread among the asperities of the 
place where they creep, they either secure it against the wind, that it is 
not so easily blown away; or else whilst they hang by it, if one stitch 
break, another holds fast, so that they do not fall to the ground.” ! 
In this way the Orbweaver proceeds, with more or less variation, until 
she has described the irregular polygon which forms the foundation of her 
snare. Each of these boundary lines, according to Blackwall’s 
tree observation, is composed of five, six, or even more united 
an threads.* It is always sharply distinguished by its thickness and 
strength, and often by its color, from the other lines of the snare. 
The upper foundation line is quite commonly much the strongest. The 
framework thus formed is braced by various cords passing diagonally from 
line to line across the corners, and some- 
times also by numerous threads attached to 
surrounding objects. The entire foundation 
thus hangs taut, and presents a framework 
having the requisite degree of strength and 
elasticity upon and within which to suspend 
the true snare, 
This work is not always done rapidly and 
as though by an engineering instinct that 
readily perceives the quickest and most ad- 
vantageous sites and courses. Often there is much preparatory pioneering ; 
the laying out or dragging out of tentative lines which appear to be to no 
purpose ; a groping or “feeling” the way, so to speak, toward the best loca- 
tion, and at last the seeming accidental determination of the frame lines. 
Of course, even under such behavior there must be a general instinctive 
movement in the direction of the polygonal or triangular outlines which 
are the prevailing forms one sees. It has been said that the 
magnified. 
ee spider seems careless about the shape of the area which the 
ecioaiinn, foundation lines inclose.4 But the fact that these two forms do 
prevail well nigh universally, places the architect’s action outside 
the pale of mere chance. Moreover, examples are frequently found of 
1 Correspondence of Ray, page 58. 
2 See an article by the author in “Our Continent,’ Philadelphia, September 27th, 1882. 
§ Blackwall, Zoological Journal, Vol. V., 1832-4, page 182. “On the Construction of the 
Nets of Geometric Spiders.” 
4 Introduction to Entomology, Kirby & Spence, Vol. I., Set XIII., page 411. 
