150 PROCEEDINGS OF THE ACADEMY OF [1879. 



May 6. 

 The President, Dr. Ruschenberger, in the chair. 

 Thirty-one persons present. 



Pairing of Spiders, Linyphia marginata. Rev. H. C. McCook 

 remarked that on the afternoon of June 14, 1878, he witnessed 

 the pairing of a male and female of Linyphia marginata at Bell- 

 wood, Blair Co., Penna. The spiders were first observed at a 

 quarter before 4 o'clock P. M. They were hanging inverted in 

 the dome-shaped nest of the species, in line with each other, and 

 about three-quarters inch apart. Each hung within a smaller 

 dome, delicately but perceptibly defined, that rose within the 

 summit. These were perhaps formed by the outspread feet draw- 

 ing down the inner surface of the dome. 



The position of these individuals seeming to indicate the act 

 of copulation, he arranged himself before them as comfortabty as 

 possible for observation. The nest was hung from the lower sur- 

 face of an end of a plank that jutted over from a pile of lumber, 

 about two and a half feet from the ground, so that, seated before 

 the nest, his face was on a level with the spiders. The male 

 reached out one foot cautiously toward the female, pulling upon 

 the threads. He turned a moment to adjust the block on which 

 he sat, and, on again looking, the' two were in embrace. The 

 female was suspended in the same position as before, although 

 turned at right angles to the line on which she hung when first 

 seen. The head of the male was laid against the sternum of the 

 female, the abdomen inclined a little upward, the forelegs inter- 

 locked with or rather interlaid upon those of the female. Both 

 spiders were suspended by threads, in the normal way. This was 

 at 9 minutes before 4 P.M. After a moment's embrace the pair 

 separated ; the female made a circuit of the lower part of the 

 dome, moving in an excited, jerking manner, then returned to the 

 summit. The male approached, the female stretching out her 

 forelegs somewhat, as he laid his two forelegs within them, which 

 position was maintained, as was the relative position of the two 

 during the entire period of copulation. The female during the 

 act remained perfectly motionless except an occasional twitching 

 of the apex of the abdomen. 



The two terminal bulbs upon the male palp were laid upon the 

 epigynum of the female, and pressed downward. From one of 

 these issued the sac, a bean-shaped organ, of a bright amber color, 

 and translucent, which shone brilliantly in the sun that fell full 

 upon it from the west. It remained thus projected, held between 

 the finger-like tufted horn of the bulb, for a brief space, was then 



