[No. 1.] SEXUAL SELECTION IN SPIDERS. 21 



is so placed as to be concealed, or, as in the Attidfc, is covered 

 with a thick layer of web, under which the mother spider re- 

 mains until the young appear, seldom leaving the nest to ob- 

 tain food. On the whole, the explanation of sexual differences 

 of color in spiders which is most conformable with facts, is that 

 the males have departed from the usual colors of the genus,^ 

 and that most probably this departure has been brought about 

 by sexual or female selection. 



Thus in the Habrocestum group the general coloring of the 

 genus is represented by the females of crislatum and auratum, 

 which are gray, with oblique whitish bands ; in viridipes there 

 is a tendency to greater concentration of color, and consequently 

 to stronger contrast, the color being blackish with yellowish 

 white bands. In peregrinum and aurcUuvi we find that the 

 males have gone still further in the same direction, the ground 

 color being deep black and the bands pure white. (Plate 1.) In 

 splendens the male has made a still greater departure from the 

 typical coloring of the genus, while the female, also departing 

 therefrom, though not in so great a degree, shows the strongly 

 contrasting black and white that is found on the males of 

 peregrinum and auratum. 



Class II. When the adult female is more conspicuous than 

 the adult male, the young of both sexes, both in color and 

 form, more closely resemble the male than they do the female, 

 especially in the earlier moults. 



This class, while it is found both in spiders and birds, 

 differs widely in the two groups, both in the number of in- 

 stances and in the causes that have produced them. While in 

 birds the number of cases in which the females are brighter is 



1 This Is the opinion of Blactwall and of Canestrlnl. Thorell, In speaking of the 

 genus Erigone (of the family Therldida', a genus that contains an immense num- 

 ber of species, says: "The study of the spiders belonging to this interesting genus 

 has hitherto been comparatively neglected, and this neglect is no doubt to be 

 attributed partly to their diminutive size, and partly to the great similarity prevail- 

 ing among the /e?na?e.s of the different species. * *" * Many a female Is sometimes 

 mated mth one, and sometimes with another male; * * * the following lists of 

 synonyms must, unless the contrary be directly stated, be considered as applying 

 only to the males, which are comparatively easily distingiilshable." Hemarks on 

 Synonyms of Swop. Spiders, p. 97. 



