328 SEXUAL SELECTION. [Part II. 



some species of Thomisus the two sexes closely resemble 

 each other ; in others they differ much ; thus in T. citreus 

 the legs and body of the female are pale yellow or green, 

 while the front legs of the male are reddish-brown : in T. 

 Jloricolens, the legs of the female are pale-green, those of 

 the male being ringed in a conspicuous manner with vari- 

 ous tints. Numerous analogous cases could be given in the 

 genera Epeira, Nephila, Philodromus, Theridion, Liny- 

 phia, etc. It is often difficult to say which of the two 

 sexes departs most from the ordinary coloration of the 

 genus to which the species belong; but Mr. Blackwall 

 thinks that, as a general rule, it is the male. Both sexes 

 while young, as I am informed by the same author, usu- 

 ally resemble each other ; and both often undergo great 

 changes in color during- their successive moults before ar- 

 riving at maturity. In other cases the male alone appears 

 to change color. Thus the male of the above-mentioned 

 brightly-colored Sparassus at first resembles the female 

 and acquires his peculiar tints only when nearly adult. 

 Spiders are possessed of acute senses, and exhibit much 

 intelligence. The females often show, as is well known, 

 the strongest affection for their eggs, which they carry 

 about enveloped in a silken web. On the whole, it ap- 

 pears probable that well-marked differences in color be- 

 tween the sexes have generally resulted from sexual se- 

 lection, either on the male or . female side. But doubts 

 may be entertained on this head from the extreme varia- 

 bility in color of some species, for instance, of Theridion 

 lineatum, the sexes of which differ when adult ; this great 

 variability indicates that their colors have not been sub- 

 jected to any form of selection. 



Mr. Blackwall does not remember to have seen the 

 males of any species fighting together for the possession 

 of the female. Nor, judging from analogy, is this proba- 

 ble ; for the males are generally much smaller than the 



