No. 1.] SEXUAL SELECTION IN SPIDERS. 17 



more conspicuous than the adult female, the young of both 

 sexes resembling the adult female, both in color and form — or, 

 at least, resembling her much more than they do the adult 

 male. A good example of this class is Phidippus johnsonii, 

 where the female has the abdomen red and black, with a white 

 base and some white dots, while that of the male is bright 

 Vermillion red with sometimes a white band at the base. The 

 young of both sexes resemble the mother until the last moult, 

 when the males assume their bright livery. Philseus militaris, 

 a very common Attus, is another illustration ; in the male the 

 cephalothorax and abdomen are bright bronze brown, the former 

 with a wide, pure white band on each upper side and a white 

 spot on the center of the head, the latter with a wide, white 

 band around the base and sides ; the female has a brown body 

 covered over with white and gray hairs, which form a more or 

 less distinct pattern of lines and spots. To give a better idea 

 of this difference, let us suppose a male bird with the body, 

 neck and head bright bronze brown, and the wings and a patch 

 on the head pure white, with a female having mottled white 

 and brown plumage. 



Hentz described the female of his Plexippus puerperus as 

 a different species under the specific name sylvanus, so little do 

 the sexes resem ble each other. Dendryphantes capitatus is another 

 species in which there are great sexual differences. As in the 

 last instance, the male and female were described by Hentz as 

 different species. We may suppose that the sexual peculiari- 

 ties of the male have been only recently acquired in capitatus, 

 since he sometimes retains the markings and color of the 

 female, these being proper to him in the immature stage. In 

 Icius palmarum the sexes are very different. We shall, later on, 

 describe the differences in the face and falces, so that here it is 

 enough to say, that in the male the whole body is bronze 

 brown, covered with short, golden down, while in the female 

 the color is rufus, with black and white markings. 



For Habrocesium splendens the colored figures of the moults 

 and the adult forms (Plate I) bring out the fact that while the 



