434 PROCEEDINGS OF THE ACADEMY OF [1881. 



of about 45°, the two fore-feet meanwhile stretched out, and groping 

 in the air, as though feeling for the presence of obstructions, of 

 enemies or of floating threads. At the same time he elevated his 

 spinnerets and emitted a line which was drawn out at great length 

 b}' the air, but secured no entanglement. The body of the spider 

 had a gentle lateral oscillation, which appeared to the observer to 

 result from a voluntary twisting of the central rope by the 

 animal, but ma}' have been caused by the air ; the effect, in either 

 case, was to give the line a wider swing, and much increase the 

 chances of entanglement. 



However, there was no entanglement, and the spider dropped 

 several inches farther down, and repeated exactlj" the process as 

 described above. This was repeated again and again, and when 

 the observer allowed the line to attach to his person the spider at 

 once proceeded to satisfy himself of the fact, and then to venture a 

 crossing. In all these actions there was evidences of a habitual 

 mode of securing transit by bridge-lines. 



During the intervals of these attempts, and indeed preceding 

 them, the spider passed back and forth along all the branching 

 twigs, leaving behind him trailed threads or lines connecting the 

 ends, many of which seemed to be purely tentative. At last a 

 central point was taken, a short thread dropped therefrom and 

 attached to one of these tentative lines. The confused network 

 of circumjacent lines was gathered together in a little flossy ball 

 at the point of union, which was now made the centre of the orb, 

 the first drop line and the two divisions of the cross line consti- 

 tuting the three original radii. From there the spider proceeded 

 to lay in the radii and complete the orb. The speaker described 

 this process in full, as illustrated by the industry of this and other 

 individuals. The time occupied in constructing the orb proper 

 was half an hour, while the work of prospecting for, and obtaining 

 a foundation consumed more than an hour. Even then the orb was 

 very irregular, and showed decided traces of the want of the usual 

 well and orderly laid foundations. An examination of a number 

 of web-sites which had been marked upon the same grounds, 

 showed that in every case where the surroundings had allowed an 

 easy and good entanglement by the wind, the spiders had made 

 webs at an early hour, and with straight and regular foundations. 



Dr. McCook concluded that the above observations, although 

 not wholly conclusive in themselves, were suflicient warrant for 

 the belief that air currents have a large part in placing the origi- 

 nal framework or foundation lines of orb-webs, and that spiders 

 habitually make use of them for that purpose. He doubted, how- 

 ever, whether there was anything like a deliberate purpose to 

 connect the point of occupancy with any special opposite point. 

 It seemed to him that the spider acted in the matter very much at 

 hap-hazard, but with a general instinct of the fact that such 

 behavior would somewdiere secure available attachments. Many 

 of her bridge lines were evidently tentative and were chiefly at 



