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THE AM ERIC AX NATURALIST [Vol. XLIV 



that some cases of brighter female coloration represent 

 examples of warning coloration, and consequently come 

 under our sixth category of secondary sexual phenomena. 



It will be recalled that Wallace (1889) explained the 

 general less conspicuous coloration of female birds on 

 the ground of their need of greater protection, since they 

 play the major role in guarding the nest and the eggs. 

 The Peckhams (1889) have argued that this idea would 

 not apply to the general inconspicuous coloration of 

 female attids, because when they have eggs they hide 

 these and themselves within thick silken nests and so are 

 sufficiently protected from enemies. But I believe Wal- 

 lace's explanation will apply in the case of spiders. For 

 the males do not develop their ornamentation until matu- 

 rity, and they have much less need of protection than the 

 females because they live usually not much longer than 

 a few weeks after maturing, and take no part in the care 

 of the young. # The males have fulfilled their main func- 

 tion after impregnating the females, and they are of no 

 use to the species thereafter. But the females live at least 

 several months after maturing, in some cases several 

 years, and they have the whole care of the eggs and young. 

 In araneads, as in all animals, the females are of the 

 greater importance in the perpetuation of the race. 

 Therefore it is probable, in agreement with "Wallace, that 

 natural selection has generally maintained a more pro- 

 tective coloration of the female. 



In all six categories of secondary sexual characters in 

 so far as spiders are concerned, accordingly, natural 

 selection alone is sufficient to explain the regulation of the 

 phenomena. At the same time these phenomena would 

 seem to have a manifold origin, as they certainly fulfill 

 very different uses. 



LITERATURE LIST. 

 1873. Canestrini. Caratteri sessuali mcond&rii degli Arachnid! Atti Soc. 



Veneto-Trentina Sc. Nat. Padova. 1. 

 1900. Cunningham, J. T. Sexual Dimorphism in the Animal Kingdom. 



