1881.] 



xVATURAL SCIENCES OP PHILADELPHIA. 



171 



sketching the arrangement of the basket stretched between the 

 feet (2, 3, 3, 4, 4, fig. 9). With this chart in one hand, and in the 

 other hand a magnifying glass focused upon the feet, I watched 

 until favored with several successive and unsuccessful springings 

 of the net. As the spider only leaves her seat when she thinks 

 that an insect is well entangled, and again bows her net by pulling 

 on the trap-line if no prey be ensnared, the above conditions en- 

 abled me to compare my chart of the basket, with the basket itself 

 as seen under the glass. I found that the outlines on the paper 

 and the lines under the animal's feet exactly corresponded. There 

 had therefore been no change in the relative positions of the hind- 

 feet, mandibles and palps, perhaps also of the second pair (2) of 



feet. There had been an ac- 

 tual (not seeming) motion of 

 the body with and in the di- 

 rection of the web, and this 

 had been caused by releasing 

 the first pair of legs (1) from 

 the trap-line. 



The importance of this 

 determination seems greater 

 from the fact that I had at first 

 concluded that the Radiosa 

 actually operated her snare 

 by sections. That is, instead 

 of springing the whole orb at 

 once, as above described, she 

 simply sprung the ray struck by an insect, by unclasping the foot 

 holding the axis of that ra3^ Thus, ray ii, fig. 9, would be sprung 

 by releasing the axis of ii, from No. 3, the third foot. This 

 is probabl}'' not done when the snare is in complete form (as 

 at figs. 1, 3, 4), but I now believe that it is done when the web 

 has been partially destroyed, and is reduced to two rays or sectors 

 as at fig. 11. This I hope to determine accurately during the 

 current summer. If it should be verified we shall have another 

 resemblance between the habits of Hyptiotes and Radiosa. 



Fig. 9. — Kay spider in position showing slack 

 coll SI, and fout-basket, 2, 3, 4. 



III. Gradual Obliteration of the Web. 



The fragmentary condition of Radiosa's web after contact with 

 insects has already been referred to. The snare is gradually 



