37 



We introduced one of the aeronautic spiders under 

 water ; but it did not appear injured ; and when with- 

 drawn, soon let itself fall by means of a thread. Placed 

 on water, at 66 F., it remained on its surface," without 

 attempting to escape by the propulsion of a thread, 

 taking repeated springs forward, then receding, and 

 patting the water rapidly with its tarsi, in the manner 

 of the squirrel. In water at 67 F., it was quiescent : 

 during repose at the bottom of a tumbler of water, 

 there issued from between the palpi an air-bell, which, 

 expanding, carried the spider to the surface ; the 

 aerial appendage thus diminishing the specific gravity, 

 and affording a striking elucidation of the habits of the 

 aranea aquatica. An aeronautic spider being put into 

 water at 94 F., remained at the bottom of the vessel, 

 sometimes at rest, sometimes locomotive. At length 

 it projected a thread upward, and by that means 

 wound itself, resting at intervals, to the surface of the 

 water : at the close of the experiment, the tempera- 

 ture had fallen to 86 F. One of these spiders, by 

 candle-light, darted instantaneously 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, the thread 

 was made to spin with great rapidity on its axis ; 

 during this period it moved gradually toward the ver- 

 tical plane, and, being thus highly twisted, formed a 

 stronger medium of escape. 



On one occasion we were making some experiments 

 with an aeronautic spider, during a warm day, and 

 brilliant sunshine, about noon ; the door of the room 

 was a-jar, and the insect, in the act of propelling its 

 threads in all directions, when it suddenly darted one 

 toward the door, in the direction of the influx-cur- 

 rent, perfectly horizontal, and in length fully ten 

 feet : the angle of vision being particularly favour- 



