CONSTRUCTION OF AN ORBWEB. 7Al 
tendrils, frequently securing an anchorage by attaching her dragline, and 
all the while holding aloof from contact with the foliage the new founda- 
tion line which is spun after her as she moves. 
Kirby and Spence describe this curious variation of the habit. A spider 
isolated upon a stick set within a vessel of water dropped from the top of 
the stick to which the usual dragline attachment had been made, 
A Varia- and emitted two threads as it descended. Having reached a point 
tion of : 3 
the Habit, 2°?" the surface of the water, it stopped, and by some unobserved 
means, severed one of the threads close to the spinnerets. The 
free end of the released filament floated up and outward from the top of 
the stick, and was caused to entangle upon a pencil held in the observer’s 
hand. The spider, which had meanwhile mounted the summit of the stick, 
perceived the line to be taut, and having tested it by pulling, crept over it to 
the pencil, dragging another line behind her as she moyed.! This isan iso- 
lated example, and may, of course, have been a simple coincidence, as it is 
not certain that the spider designed to secure a bridge line by the above 
behavior. Yet it is worthy of notice as suggesting a line of observation 
that may yield good results. 
Il. 
We may now construct the diagramatic figure, Fig. 67, to show the proc- 
ess by which an orb frame is laid when the prime foundation is obtained 
by an air current. We suppose that an Orbweaver in the act of web- 
making has stopped upon the leaf at the left of the cut. Turning. her 
abdomen toward the course of the wind, she issues a line (a, a) that floats 
outward until it entangles at x. This fact is at once perceived, and the 
spider (ss) ventures over it as at bb, dragging behind her a thread which 
unites with and strengthens the original line, which had been drawn taut, 
as e, ¢, ¢, x. This may be repeated several times, until, at last, the prime 
foundation line is formed. 
This strengthening by means of overspinning is not necessarily, perhaps 
not generally, done in immediate succession of threads, but from time to time. 
At various stages of working in the radii of other parts, the crea- 
ture seems to perceive the need of strengthening the supporting 
lines, and proceeds to stretch a new strand or two. Then she re- 
sumes work upon the orb, to return as occasion requires, and adds strands 
to her cable. When the upper line is completed, especially if it be one which 
has been used for several days, it presents the appearance of a white or 
yellowish white thread as thick as a bit of sewing silk. It may readily be 
reeled upon a stick or spool, and its numerous filaments can be seen and 
eyen separated. It has a glossy appearance, and may often be found sey- 
eral feet in length. 
First 
Line. 
1 Introduction to Entomology, Volume 1, set XIII., page 415. 
