72 AMERICAN SPIDERS 



spiders, Gasteracantha and Micrathena, the females even have beau- 

 tifully painted and sculptured bodies. 



SPERM INDUCTION 



The strange process by which the male spider transfers semen 

 from the primary genital organs into the receptacles of the palpi is 

 called "sperm induction." It was observed for the first time in 1843, 

 by Anton Menge, who described how the male constructed a little 

 web of silk, desposited a droplet of sperm upon it, and then applied 

 his palpi to the drop until it was entirely absorbed into these latter 

 organs. It is not at all surprising that this extraordinary action was 

 doubted at first by many people, among them several eminent 

 arachnologists, who insisted that there must be an internal connec- 

 tion between the testes, deep in the abdomen, and the tips of the 

 palpi. Now we recognize sperm induction as only the first step in 

 a series of strange acts that mark the sexual life of spiders. 



Sperm induction is of necessity a very common phenomenon, but 

 one must be on hand at the right time to observe it. Soon after the 

 male becomes sexually mature, he charges his palpi and is then 

 ready to wander about in search of a mate. This is an act which is 

 not part of the previous experience of the male, but' is initiated by 

 internal changes in the body associated with the arrival of maturity. 

 He performs it instinctively and perfectly at the outset, because it 

 is fixed in his behavior as a racial memory. Thereafter, he fills his 

 palpi frequently, usually immediately following copulation, which 

 is the best time to see this interesting spectacle. A few spiders are 

 able to mate more than once without exhausting their semen; others 

 have to pause during their mating to refill the bulbs. 



There is considerable diversity in the manner in which different 

 types of spiders accomplish sperm induction. In no known instance 

 is the sperm taken directly from the genital opening at the base of 

 the abdomen, which would appear to be a logical means of solving 

 the problem, and would be physically possible in many spiders with 

 long palpi. Some spiders spin very simple, loose webs and absorb 

 the semen by placing the palpi directly against it. In Pholcus a 

 single silk line between the third legs is drawn across the genital 

 opening until the spermatic globule adheres to it, whereupon it is 

 taken up by the chelicerae and held there for direct absorption by 

 the palpi. Some of the other primitive spiders do essentially the 



