No. 2.] PROTECTIVE RESEMBLANCES IN SPIDERS. 101 



one sex alone, have incessant!)' been taken advantage of and 

 accumulated through sexual selection in relation to the repro- 

 duction of the species; therefore, it appears at first sight an 

 unaccountable fact that similar variations have not frequently 

 been accumulated through natural selection, in relation to the 

 ordinary habits of life. If this had occurred the two sexes 

 would often have been differently modified, for the sake, for 

 instance, of capturing prey, or escaping from danger. Differ- 

 ences of this kind between the two sexes do occasionally occur, 

 especially in the lower classes. But this implies that the two 

 sexes follow different habits in their struggles for existence, 

 which is a rare circumstance with, the higher animals."* 



In the Gasteracanthidse we have the necessary conditions 

 for the production, by natural selection, of a difference between 

 the sexes early in life, i. e., the habits of the sexes are distinctly 

 different, the males living in some place of concealment, while 

 the females soon begin to sit exposed in the web. It is 

 naturally of the greatest importance that the young females, 

 while adopting the habits of the adults, should acquire also her 

 special protection of form and color. 



The variation in the female, although entirely due to 

 natural selection, probably first occurred in the adult, since 

 variations occurring early in life tend to be inherited by both 

 sexes. 



MIMICRY. 



Mimicry, or the imitation of animal forms, while it is a 

 form of indirect protection, differs in no essential respect from 

 the imitation of vegetable and inorganic things. As Bates has 

 said, the object of mimetic tendencies is disguise, and they will 

 work in any direction that answers this purpose.f 



In nearly all respects spiders come under the three laws 

 given by Wallace, as governing the development of mimetic 

 resemblances in several large classes. These laws are as follows : 



1. In an overwhelming majority of cases of mimicry, the 



*Loc. clt., p. 241. 



iLepidoplera of the Amazon Valley, Trans. Linn. Soc, Vol. XXIU. p. 5U. 



