308 THE DESCENT OF MAtf. 



I am informed by Mr. Blackwall that the sexes while young 

 usually resemble each other; and both often undergo great 

 changes in color during their successive moults before 

 arriving at maturity. In other cases the male alone appears to 

 change color. Thus the male of the above bright-colored 

 Sparassus at first resembles the female, and acquires his pecu- 

 liar tints only when nearly adult. Spiders are possessed of 

 acute senses, and exhibit much intelligence; as is well 

 known, the females often show the strongest affection for 

 their eggs, which they carry about enveloped in a silken 

 web. The males search eagerly for the females, and have 

 been seen by Canestrini and others to fight for possession of 

 them. This same author says that the union of the two 

 sexes has been observed in about twenty species; and he 

 asserts positively that the female rejects some of the males 

 who court her, threatens them with open mandibles 

 and at last after long hesitation accepts the chosen ona. 

 From these several considerations, we may admit with some 

 confidence that the well-marked differences in color between 

 the sexes of certain species are the results of sexual selection, 

 though we have not here the best kind of evidence the 

 display by the male of his ornaments. From the extreme 

 variability of color in the male of some species, for instance 

 of Tlieridion lineatum, it would appear that these sexual 

 characters of the males have not as yet become well fixed. 

 Canestrini draws the same conclusion from the fact that the 

 males of certain species present two forms, differing from 

 each other in the size and length of their jaws; and this 

 reminds us of the above cases of dimorphic crustaceans. 



The male is generally much smaller than the female, 

 sometimes to an extraordinary degree,* and he is forced to 

 be extremely cautious in making his advances, as the 

 female often carries her coyness to a dangerous pitch. 

 De Geer saw a male that "in the midst of his preparatory 

 caresses was seized by the object of his attentions, envel- 

 oped by her in a web and then devoured, a sight which, as 



* Aug. Vinson (" A ran Sides des lies de la Reunion," pi. vi, figs. 1 

 and 2) gives a good instance of the small size of the male, in Epeira 

 nigra. In this species, as 1 may add, the male is testaceous and the 

 female black with legs banded with red. Other even more striking 

 cases of inequality in si/e between the sexes have been recorded 

 ("Quarterly Journal of Science," 1868, July, p. 429); but. I have not 

 seen the original account. 



