216 



AMERICAN SPIDEKS AND THEIR SPINNINGWORK. 



248. Migration instinct. F, fence of netted line.'<; 

 points of first departure; B, bridge lines for transit; 

 assembly of spiderlings. 



1, 2, 3, 

 n, final 



test tlie effect of a current of air, I slightly raised an adjoining window, 

 admitting a liglit play of wind across the fence on the column x. In 



three minutes two lines 

 were fastened upon the cap 

 of the j)uppet, and two spi- 

 ders had begun to cross 

 from the points marked 2, 

 o. These lines were so del- 

 icate that I had not seen 

 them until the motion of 

 the spiders along invisible 

 bridges directed particular 

 attention to the spots. 

 Within an hour all the 

 colony but two had crossed 

 over the fence (F) to the 

 puppet, and were swarmed around the head, face, and chest of the figure, 

 and upon a mass of lines (n) that stretched to a wire (w). A triangular 

 bridge of lines (B) had now been formed, whose apex was 

 rioue*' the head of the puppet (z), and which broadened out, touching 

 Habit. *'^® columns (y and x) and connecting with the first perpendic- 

 ular bridge (F) by the three principal points (1, 2, 3) from which 

 the migration had proceeded. 



In the course of three days, by arranging various elevated objects over 

 the table, and breaking off the threads that floated beyond the prescribed 

 limits, I had induced the brood to cover a space having a linear boundary 

 of about twelve feet. The greater portion of the area thus bounded be- 

 came at last sheeted by a web composed of the innumerable lines emitted 

 by the little spiimers, so that the whole presented a quite good miniature 

 of the canvas tents of a traveling circus company. 



For long periods the little creatures would hang quite still, separated 

 from each other by distances varying from three-fourths of an inch to 

 one, two, and three inches. In these rest- 

 ing moments they hung inverted between 

 two lines which they grasped re- 

 in Rest spectively by the four feet on 

 either side; the abdomen was 

 elevated somewhat, a short thread issued 

 from the spinnerets, and was attached to 

 an upper line, thus helping to support the 

 body. (Fig. 249, 1.) Occasionally the two 

 hind legs grasped a cross line hung upon or above the parallels, and the 

 thread from the spinnerets was also attached to the cross line. (Fig 

 249, 2.) 



Fig. 249. Position of spiderlings when at 

 rest upon assembly lines. 



