COLOR AND THE COLOR SENSE. 



351 



Sum- 

 mary : 

 Color 

 Causes. 



the several groups of refracted rays, and perceives them as an unliroken 



band of metallic green color. 



These cursory examinations appear to suggest that the structural causes 



of color in si)iders are probably tlie following : First, color stains diffused 

 throughout the tissues ; second, pigment granules of various hues 

 distributed beneath the skin ; third, pigment bodies or chromat- 

 ophores ; fourth, the reflection of light from the surfaces of 

 thickly overlaid or thatched hairs ; fifth, by hairs of various col- 

 ors and peculiar forms, in some degree analogous to the scales 



of the Lejiidoptera ; sixth, certain colors, particularly the brilliant metallic 



colors, are produced by refraction of light from broken or ridged surfaces 



of the epiderm, that appear to act as prisms. 



Little attention has been paid to the structural causes of color in spiders, 



and scarcely more to the form of the color hairs, and the manner in whicli 



they are grouped and overlaid in order to 



form the various color spots and pattern 



outlines produced exclusively or in part by 



them. The subject jnight well repay tlie 



careful study of tlie microscopist, and it 



may often be found that these color hairs 



will show many varying forms, correspond- 

 ing with genera or even species. 



Mr. Emerton says ^ that the hairs or 



"scales" usually found on the Drassida; 



and Agalenidaj are feathered.^ Each scale, 



as far as he had noticed, is uniformly colored. Along the edges 

 of the red spot in Geotrecha crocata, for example, red and black 

 scales are mixed, but each scale is either all red or all black. 



-.;^ 



f 



Fig. 310. 



FIG. 313. 



Fig. 311. Fig. 312. 



Micaria longipes. 

 Figs. 310 and 313. White scales from spots 

 on abdomen. Fig. 311. Scale from hind- 

 er half of abdomen. Fig. 312. Scale from 

 front of abdomen. (After Emerton.) 



Color 

 Scales 



The scales of Micaria longipes ^ are either white or brown. The irides- 

 cence of the nlxlonicn, whicli is very marked in certain lights, he had seen 

 on the individual scales. In general form these hairs resemble those which 

 I have seen on Phidippus morsitans. 



1 In a letter to the author. 

 ^ Id., plate iii.. Fiir. 1. 



2 See New Eug. Drassidje, plate iii.. Fig. 3, e. 



