BIOLOGICAL MISCELLANY. 67 
‘of her hub, and is in the following manner: The body is bowed or 
arched a little more than is usual when in that position, and then is set 
. _ In motion in such wise as to cause the web to move back and 
i Body forth swinging upon its foundation lines. The motion is at first 
slow, and is rapidly increased until communicated to the whole 
web, which is oscillated at times so violently that the form of the spider 
becomes indistinct. This motion is continued for several minutes, the 
period varying in length. Mr. Muybridge, distinguished for his observa- 
tion upon the motions of animals, informed me that he once watched a 
female Argiope cophinaria in continuous oscillation on her snare for a 
half hour. 
The oscillation of the orbs by Argiope appears to be accomplished by 
lifting the abdomen up and down, or rather back and forth, from the web, 
and the alternate slackening and drawing taut of the line which connects 
the spinnerets with the central silken shield. At the same time the legs 
are alternately bent together and stretched out, thus drawing the orb in 
and repelling it. These movements of the spider of course put the orb in 
oscillation, and when rapidly repeated it moves back and forward with 
great rapidity. 
Among Lineweavers this habit takes the form of a rapid whirling of 
the body within the snare. The species most addicted to this habit is our 
common long legged cellar spider, Pholeus phalangioides. This 
creature hangs upon its snare of large loosely netted cross lines 
with its back downwards. Its feet, which are stretched upward 
from the body, by reason of the great length of the legs clasp 
these lines well together. Then begins a circular motion of the body. 
This at first is slow, but is rapidly increased until the body whirls around 
in circles so rapidly that it can scarcely be distinguished from the whole 
mass of agitated lines, legs, and body, which resembles a revolving cone. 
The manner in which the motion is produced is probably the same in 
both tribes here mentioned, but the nature of the Orbweaver’s web is such 
that the motion is limited by the upper and lower foundation lines within 
which it is set, and is so compounded as to compel the orb to a lateral or 
pendulum like movement; that is, a movement perpendicular to the plane 
of the orb. In the case of ‘Pholeus, however, the web of right lines per- 
mits the body to revolve in circles which are parallel to the plane of the 
horizon. 
This habit is doubtless protective, and probably serves to confuse attack- 
ing Hymenoptera, birds, and other enemies, and thus avert their aim or 
drive them from the position by the unwonted agitation of the 
Uses of 
the Habit, We? But its origin and chief purpose are probably connected 
with the taking of prey. The swaying of the web must aid to 
entangle more completely a victim which strikes it, since it stimulates the 
captive to increase its struggles and thus more effectively to fasten itself to 
Whirling 
Move- 
ment. 
