THE AERONAUTIC OR BALLOONING HABIT. 265 



found them to be lupi [Lycosids], which seldom or never enter houses, 

 and cannot be supposed to have taken their flight from the steeples." 1 I 

 once found a number of half grown Epeiras upon their round webs on 

 the topmost railing of the dome of St. Peter's at Rome (Italy), whither 

 they or their maternal ancestor had doubtless been carried by the wind 

 from the surface of the earth. 



October 25th, 1883, was a bright day following a series of cold, wet 

 days caused by a severe northeast storm. At noon, while crossing the 



Chestnut Street Bridge, Philadelphia, I saw a great number of 

 ~ aeronautic threads floating in the air, streaming from the tips of 



the bridge balustrade and lodged upon the piers. One of the 

 threads, a long filament, was sailing slowly toward the river as a Pennsyl- 

 vania Railroad train dashed along the river track beneath the bridge. It 

 was low enough to strike the cars as they rolled by, and so was carried 

 on southward with its tiny voyager another illus- 

 tration of how artificial habits of man tend to 

 the geographical distribution of life. The filaments 

 were long, pure white, curled or wrinkled, about 

 one millimetre wide or less, occasionally expanded 

 into thicker wads, and frequently carried attached 

 to them minute insects which had doubtless en- 

 tangled in the fibres as the threads floated in the 

 air. (Fig. 280.) On one thread I found three, 



FIG. 276. Young spider sending 



on another two small flies. The young balloonist out aeronautic threads while 

 is thus provided with food upon his landing, if hanging upon a web " 

 he choose to avail himself of these chance supplies. The insects are sim- 

 ply entangled, as the fibre is without viscidity. 



The field observations recorded above have been confirmed by numer- 

 ous studies made with spiderlings reared in the house, especially the young 



of Epeira sclopetaria, Epeira domiciliorum, Epeira insularis, and 

 oung- Agalena nasvia. As the results obtained were not different from 



those already given, they require but brief mention. When let 

 loose into the air from the finger tip, the spiderlings floated out by a sin- 

 gle thread, which was always and instantly first attached to the finger. 

 At first the head was outward, the abdomen being turned toward the hand, 

 from the apex of which the long superior spinnerets of the tubeweavers 

 diverged. Presently the little creature turned and cast out a thread be- 

 hind, when, if permitted, it would usually clamber up the original thread 

 to the finger. When this was broken off, the spider, seated midway of 

 the two filaments, floated off and outward, and was lost to sight. Again, 

 by an eddy of the air, the thread would be thrown backward and upward 

 and catch against the wall, upon which the little voyager would anchor. 



1 Correspondence of John Kay, page 77. Lister to Kay, January 20th, 1670. 



