INVERTEBRATA, CRYPTOGAMIA, MICROSCOPY, ETC. 5(Jl 



meslies in a fisherman's net. The diameter of the dome was from seven 

 to eight inches at the base, the height nearly the sa,me. It was sus- 

 pended in the midst of the mass of right lines by silken guys of like 

 character, which thoroughly steadied the delicate structure, and per- 

 fectly preserved its form. Beneath the dome, from two to three inches 

 removed, was a light sheet of cobweb c, irregularly meshed, of waving 

 and straight lines. It had a decided convexity upward, and was 

 supported, like the dome above it, and of which it seemed to be a 

 protecting curtain, by silken threads or guys, so stretched as exactly 

 to meet this purpose. 



This spider seems to form a perfect link between the orb-weaving 

 and the line-weaving spiders in the characteristic spinning work of the 

 two groups, and the main object of the paper, which is illustrated by 

 nine woodcuts, is to exhibit this fact. 



Aeronautic Flight of Spiders.*— In 1877 the Rev. H. C. McCook 

 published! some observations on the ballooning habits of spiders, 

 which he now supplements by several important items, and which he 

 considers make quite complete the mode of ballooning, at least among 

 the citigrade, and perhaps also the saltigrade spiders. 



The whole process may be briefly given as follows : — 1. The 

 spider seeks a high position, as the top of a fence post, as the point of 

 ascent ; 2. The abdomen is elevated to as nearly a right angle with 

 the ccphalothorax as may be ; 3. A pencil of threads is emitted from 

 the spinnerets, the face being meanwhile turned to various points 

 until it looks in the direction of the wind ; 4. The legs are sti*etched 

 upward, thus raising the body aloft ; 5. They gradually incline in the 

 dii'ection of the breeze, the joints straighten out, the legs sink forward 

 and down till the first pair are almost on a level with the post, the 

 whole attitude of the animal being that of one resisting some force 

 exerted from above; 6. Suddenly a. id simultaneously the eight claws 

 are imloosed, and the spider mounts with a shai'p bound, apparently, 

 7, and floats off with the back downward generally, but sometimes 

 with this position reversed ; 8. At first the abdomen seems to be in 

 advance, but generally the body is turned so that the head rides in 

 front ; 9. The pencil of threads is caught apparently by the feet, and 

 floats out in front, upon which, 10, sometimes the spider will climb 

 upward, as though to adjast the centre of gravity; 11. Meanwhile a 

 thread or pencil of rays issues from the spinnerets, which floats out 

 behind, leaving the spider to ride in the angle of the two pencils, or 

 12, as it sometimes happens of three which diverge widely at the 

 upper free ends ; 13. The feet seem to be united by delicate filaments, 

 which would serve to increase the buoyancy of the balloon ; 14. The 

 spider is now carried forward by the wind, riding for long distances in 

 an open sjiace, and often borne high upwards upon ascending currents ; 

 15. Its anchorage appears at times to be in its own volition, by drawing 

 in with the claws the forward pencil, and gathering it in a white roll 

 within the mandibles, but 16, most frequently the balloonist is 

 stopped by striking against some elevated object, or by the subsi- 



* ' Proc. Acad. Nat. Sci. Phila.,' 1878, p. 337. f Ibid., 1877, p. 308. 



