57 



twean clapboards, etc., and may be seen on the sunny side 

 of the house, and in the hottest places, wandering in search 

 of prey. It moves with agility and ease, but usually with a 

 certain leaping gait. The moment, however, it has discovered 

 a fly, all its motions are altered ; its cephalothorax, if the fly 

 moves, turns to it, with the firm glance of an animal which can 

 turn its head ; it follows all the motions of its prey with the 

 watchfulness of the falcon, hurrying its steps or slackening 

 its pace, as the case may require. Gradually, as it draws 

 near to the unsuspecting victim, its motions become more com- 

 posed, until, when very near, its movements are entirely im- 

 perceptible to the closest observation, and, indeed, it would 

 appear perfectly motionless, were it not for the fact that it 

 gradually draws nearer to the insect. When sufficiently near, 

 it very suddenly takes a leap, very seldom missing its aim. 

 I saw one, however, make a mistake, for the object which it 

 watched was only a portion of the wing of an hemipterous 

 insect entangled in a loose web. It took its leap and grasped 

 [355] the wing, but relinquished it immediately, apparently 

 very much ashamed of having made such a blunder. This 

 proves that the sight of spiders, though acute, is not uner- 

 ring. Before leaping, this Attus always fixes a thread on the 

 point from which it departs ; by this it is suspended in the 

 air if it miss its aim, and it is secure against falling far from 

 its hunting grounds. 



These spiders, and probably all other species, a dav or two 

 before they change their skin, make a tube of white silk, open 

 at both ends ; there they remain motionless till the moulting 

 time arrives, and, even some days after, are seen there still, 

 probably remaining in a secure place, for the purpose of re- 

 gaining strength and activity. 



Habitat. Throughout the United States. 



[PI. 18, fig. 74, eyes ; fig. 90, tropin. Supplement. ] 



[¥, length 10.5 mm.; cephalothorax 4.4 mm.; legs 9, 7.8, 7.8, 9. 

 <S " 10mm. " 4.6mm.; " 11.5,9.3 8.9.8. 



