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THE AMEBIC AX XATUB ALIST [Vol. XLIV 



before the females." There may be more fighting be- 

 tween males when females are present, though there is no 

 good evidence on this matter; but we have no reason to 

 suppose that the males consciously endeavor to exhibit 

 their prowess any more than they consciously try to dis- 

 play their ornaments. Males of the attid Icius palmarum 

 placed in small cages were not observed by me to fight, 

 nor were males of Phidippus mccookii nor those of Zygo- 

 ballus bettini; but fighting of males was noticed in Cera- 

 tinopsis interpres, Geotrecha pinnata and Xysticus nerv- 

 osus, and in the last species a male would leave the back 

 of a female to fight a rival. But, as the Peckhams found, 

 no injuries result to the males from this fighting, there- 

 fore these are not serious combats, and only once have I 

 seen a male kill another male of his species (in Pros- 

 thesima atra). 



Male spiders also do not possess intimidation organs, 

 which result when weapons become hypertrophied accord- 

 ing to the views of Guenther (1909). 



2. Characters for sexual recognition and stimulation 

 may be subdivided according to the sense organs which 

 they affect, as Jager "(1874) has indicated. As we have 

 seen, the only senses concerned in the case of spiders seem 

 to be those of touch and sight. It may be that certain 

 of the tactile organs, probably certain of the jointed 

 spines, may become more numerous or more specialized 

 at maturity to aid in sexual recognition, but this point re- 

 mains to be tested. But those secondary sexual charac- 

 ters of male spiders found only where there is courtship 

 by sight, such as ornamental colors and structures, and 

 posturings that display them, fall under this category. 

 Such are the male differences, as the Peckhams have 

 shown, in the chelicera, clypeus, palpi and legs, that is, 

 "in those parts of the animal that are plainly in view 

 when the male is paying court to the female." Thus the 

 chelicera may be lengthened, curved or spinous; the 

 ciypeus may be heightened or hem- prominences; the first 

 pair of legs may be thickened or have tufts of hairs ; and 

 any or all of these parts may have conspicuous color 



