68 Miscellaiieous. 



How Orh-weaving Spiders mal-e tlte Frameworl: or Foundations 

 of Webs. By the Rev. Dr. H. C. McCook. 



Eev. Dr, H. C. McCook said that he had given attention during 

 the past summer to the mode of constructing webs prevailing among 

 orb-weaving spiders. He had been led to make some special studies 

 of the extent to which air-currents are utilized iu la3-iag the foun- 

 dation-lines upon which the orbs are hung by a remark of Rev. 0. 

 Pickard Cambridge in his work on the Spiders of Dorset*. 

 "Spider-lilies," he says, "may frequently be observed strained 

 across open spaces of many feet and even yards in extent. This has 

 been explained by some naturalists to have been done by the help 

 of a current of air carrying the thread across. I cannot, of course, 

 say that it has never been thus effected, though I have certainly 

 never myself witnessed it. I have, however, on several occasions 

 seen a spider fix its line, then run down to the ground, across the 

 intervening space, and so up the opposite side, trailing its line as it 

 went ; and then having hauled in the slack, it fixed the line to the 

 desired spot. This I believe to be the usual mode of proceeding in 

 such cases." 



Dr. McCook was satisfied that on both the above points this dis- 

 tinguished araneologist had failed to possess himself of all the facts ; 

 but he took up tlie points in ([uestion anew during the summer, and 

 made notes of liis studies. His previous opinion was fully confirmed. 

 He had in a great number of cases observed orb-weavers passing 

 from point to point by means of lines emitted from their spinnerets 

 and entangled upon adjacent foliage or other objects. These mimic 

 " wire-bridges " were of various lengths, owing to the direction of 

 the wind and the relative positions of the spider and the standing 

 objects around it. Lines of two, three, and four feet were frequent ; 

 lines of from seven to ten occurred pretty often ; he had measured 

 one twenty-six feet long, and in several cases had seen them strung 

 entirely across country roads of from thirty to forty feet. Many of 

 these lines he had seen carried by the wind directly from the spiders' 

 spinnerets, had observed the entanglement, had seen the animal 

 draw the threads taut and then cross upon them. That all the 

 lines were similarly formed and used he had no doubt. 



It was more diflicult to determine the other question, viz. whether 

 the lines used for the foundations of orb-webs were formed iu the 

 same way. Undoubtedly such lines are often made precisely as 

 asserted by Mr. Cambridge. Dr. McCook had many times observed 

 this ; he had seen an orb-weaver after traversing a considerable 

 space by a series of successive bridge-lines settle upon a site between 

 the forked twigs of a bush, and carry her foundation- lines around 

 in the manner described. Eut, on the other hand, he was prepared 

 to say that the air-laid bridge-lines were also used for the founda- 

 tions or f]-ames of orbs. 



J . First, he had observed that the hours in the evening at which 



* Vol. i., IiUrodiicticn, p. xxi. 



