1 78 Evolution and Adaptation 



from each other in color, the males are often of a darker shade 

 than the females. " In some species, however, the difference 

 is conspicuous ; thus the female of Sparassus smaragdulus is 

 dullish green, whilst the adult male has the abdomen of a fine 

 yellow with three longitudinal stripes of rich red." Darwin 

 believes that sexual selection must take place in this group, 

 because Canestrini has observed that the males fight for the 

 possession of the females. He has also stated that the 

 males pay court to the female, and that she rejects some of 

 the males who court her, and sometimes devours them, until 

 finally one is chosen. Darwin believed, on this evidence, 

 that the difference in color of the sexes had been acquired 

 by sexual selection, "though we have here not the best kind 

 of evidence — the display by the male of his ornaments." 

 This evidence has, however, now been supplied through 

 the interesting observations of Mr. and Mrs. Peckham. 

 These accurate observers have studied the courtship of the 

 male, and observed that during the process, he twists and 

 turns his body in such a way as to show to best advantage 

 his colors to the female. From their account this certainly 

 appears to be the result of his movements, but whether this 

 is really the case, and whether the female makes any choice 

 amongst her suitors, according to whether they are more or 

 less brilliantly marked, we are absolutely ignorant. The fol- 

 lowing account given by Darwin should not pass unnoticed: — 

 " 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, enveloped by her 

 in a web and then devoured, a sight which, as he adds, filled 

 him with horror and indignation.' The Rev. O. P. Cam- 

 bridge accounts in the following manner for the extreme 

 smallness of the male in the genus Nephila. ' M. Vinson 



