1903.] NATURAL SCIENCES OF PHILADELPHIA. 145 



and not because he would a}:)peal to her as more beautiful or graceful 

 than other males. 



These views as to the origin and meaning of courtship in spiders 

 may be briefly summarized as follows : The mature male is stimulated 

 to great excitement by a perception, visual and tactual, of a mature 

 virgin female, and this excitement finds its expression in muscular 

 movements. The male does not immediately embrace the female, 

 for in most spiders he is the weaker individual, but delays in order to 

 first determine whether the female is eager or hostile. Rhythmically 

 repeated motions of the male during this period of delay constitute 

 courtship, and these motions are for the most part exaggerations of 

 ordinary motions of fear and timidity. By such motions he adver- 

 tises himself to the female as a male, but there is no proof that he 

 consciously seeks to arouse her eagerness by aesthetic display. That 

 male is accepted by the female who most quickly and surely announces 

 himself, by his rhythmic movements, to be a male; and thei'e seems 

 to be no good reason to hold that the female is actuated in her choice 

 by sensations of beauty. If such a process be interpreted as sexual 

 selection, it would be a selection of the male who most determinedly 

 announces himself to be a male, and not as the male who appeals to 

 the female as the inost beautiful. 



Post-nuptial moult. — It is generally believed that in araneids the 

 final moult precedes the mating. But Bertkau (1885) has shown that 

 in Atypus piceus a moult, with change of the seminal receptacles, 

 occurs after the first year of oviposition; and I have described here 

 for Lycosa ocreata pulchra a moult following a successful copulation. 

 Accordingly, in some cases a moult may follow the mating ; and prob- 

 ably this will be found to be general in species that five several years, 

 since increase in body size occasioned by rich feeding would appear 

 to necessarily induce further moults. 



Wagner (1888) has described the histological changes of moult. 

 I would simply add here that the moult in all the spiders observed by 

 me follows the same plan: a horizontal split of the old skin along the 

 sides of the abdomen and of the cephalothorax (here just above the 

 legs and the jaws), so that the skin breaks into a dorsal and ventral 

 piece. This is quite different from the process of moult in insects and 

 crustaceans. 



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