HORIZONTAL SNARES AND DOMED ORBS. 



159 



they precipitate themselves from their snares to the ground, I prepared 



to draw my specimen upward by her dragline, feeling sure that I would 



certainly capture her, when, to my amazement, she threw herself upon 



the surface of the water, a distance of eight or ten feet. I looked to see 



her drown, or at least to be swept away through the open sluice gate by 



the fast rushing stream. Neither of these things happened. The 



moment our Stilt spider struck the water she reached upward 



one hind leg, clasped the dragline in her claw, and began to 



scurry over the mill race toward the shore. 



I watched the movement with exceeding interest, and was delighted to 

 see the adventurer reach her destination. (See Fig. 151, right hand figure.) 

 The dragline, partly by its natural elas- 

 ticity, but also because the spider prob- 

 ably reeled out thread as she traveled, 

 continued to stretch as the spider moved 

 toward the shore. It thus held her firmly 

 anchored to the surface of the plank to 

 which her dragline was attached, so that 

 the force of the current, thus counteracted, 

 did not sweep her through the open sluice 

 over the shoot. In the meantime her feet 

 were kept in motion, and she appeared to 

 me to be walking the water in the man- 

 ner of certain so-called " water spiders," 

 belonging to the genera Dolomedes and 

 Lycosa of the Citigrades. It certainly is 

 an interesting fact in the natural history 

 of an orbweaving spider, that it possesses 

 a habit so closely resembling one charac- 

 teristic of a tribe widely separated from it 

 in nearly every other respect. 



The outspun filaments that serve the 

 spider for navigating the air are also utilized for propulsion over the 

 water. In one case they serve as a balloon, in the other as a 

 sail. This discovery was made on a pleasant October day while 

 walking along the shore of Deal Lake, Asbury Park, New Jer- 

 sey. 1 I stopped before a clump of tall grass that grew upon a little 

 tongue of land that jutted into the lake, in order to shake down from the 

 foliage any spiders who might for the time be domiciled thereon. The 

 especial object of my search was water frequenting species, particularly 

 the common Dolomede (Dolomedes sexpunctatus), whose mode of run- 



1 October 21st, 1881. I believe that I have the honor to be the first person who ob- 

 served, or at least announced, this interesting behavior. See a note published in " The 

 Continent," Philadelphia, August 2d, 1882. 



FIG. 151. Tetragnatha hanging extended, and 

 running on water. 



Navigat- 

 ing "Water 



