390 ON THE ASCENT OF THE SPIDER 
but though it remained there upwards of a minute, it did 
not appear injured thereby ; and when withdrawn, soon 
let itself fall from a point, by means of a thread. 
Posited gently on water, at 66° Fahrenheit, it remained 
on its surface, without attempting to escape by the propul- 
sion of a thread. It took repeated springs forward, and 
then receded, patting the water rapidly with its tarsus, in 
the manner of the squirrel. 
In water at 67° Fahrenheit, it was quiescent. When re- 
posing at the bottom of a tumbler of water, there issued 
from between the palpi an air-bell, which, expanding, car- 
ried the spider to the surface ; the aerial appendage thus 
diminishing the specific gravity of the aggregate, and af- 
fording a striking elucidation of the habits of the Aranea 
aguatica. 
An aeronautic spider being put into water at 94j° Fah- 
renheit, remained at the bottom of the vessel, sometimes at 
rest, sometimes locomotive. It projected a thread upward, 
and by that means, sailor-like, wound itself, resting at in- 
tervals, to the surface of the water. At the close of the ex- 
periment the temperature of the fluid had fallen to 86° F. 
One of these spiders, by candle-light, darted instantane- 
ously a thread to the ceiling of the room (eight feet high) ; 
it described an angle of about 80° with the horizon. By 
means of the combined act of the tibia and tarsus, " guid- 
ing them wittingly," the thread was made to spin with 
great rapidity on its axis ; and during this period it moved 
gradually toward the vertical plane, and, being thus highly 
twisted, formed a stronger medium of escape. 
During my stay at Chester, while I was experimenting 
with an aeronautic spider, during a warm day, and brilliant 
sunshine, about noon ; when my room-door was a-jar, and 
the insect in the act of propelling its threads in all direc- 
tions, it suddenly darted toward the door, in the direction 
