COURTSHIP AND MATING 95 



in females with a single terminal claw, while in the males it is en- 

 larged and transformed into a copulatory organ. 



The spider's palpus is undoubtedly the most unusual intromittent 

 organ that has been developed in any group of animals; its parallel 

 is found only in some crustaceans, in dragonflies, and in the rare 

 arachnids of the order Ricinulei. The whole process of its employ- 

 ment is a complicated one, requiring detailed, elaborate acts and 

 routines before it is successful. What do we know about the devel- 

 opment of this curious mode of copulation? There is no recapitu- 

 lation of its origin and evolution in the lives of spiders themselves. 

 Nevertheless, nature usually accomplishes new things by small steps 

 and leaves behind traces of the path that has been followed, omitting 

 only a few missing links to be filled in by speculation. T. H. Mont- 

 gomery and various other araneologists have attempted to outline 

 the spider's path, and they have all followed the same line of rea- 

 soning. 



Mating among the earliest spiders or their precursors must have 

 been by means of direct contact of the genital openings. In insects 

 and in some arachnids as well, the male intromittent organ is directly 

 connected with the vas deferens, and through this tube courses the 

 products of the testes. The scorpions appress their abdomens close 

 together, effecting the transfer by means of an eversible copulatory 

 organ. This same habit is found in the harvestmen, but the intro- 

 mittent organ is usually a long tube that conveys the semen. The 

 prime step toward araneid copulation is that of voiding a sperma- 

 tophore and then transferring it by means of an appendage, thus 

 doing away completely with direct copulation. The male solpugid,. 

 one of the most primitive of all arachnids, seizes the female, and,, 

 by pinching her abdomen, causes her to fall into a state of torpor,, 

 whereupon he ejaculates and transfers the semen to her receptacle 

 with his chelicerae. Among the pseudoscorpions, the male grasps, 

 the hands of the female in his and pulls her back and forth in a 

 courtship dance, displaying at the same time the ram's horn organs 

 at the base of his abdomen. When the female is sufficiently stimu- 

 lated and responds with the necessary dancing movements, the 

 male lets go her hands and extrudes a globule of semen or sperma- 

 tophore that is attached to the floor by a thread and stands free 

 on this line. At just the right moment, when the female dances over 

 the spermatophore, the male grasps her genital cleft with his stout 

 front legs and forces the drop into the aperture. Comparable habits. 



