COLOR AND THE COLOR SENSE. 



351 



Sum- 

 mary: 

 Color 

 Causes 



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

 band of metallic green color. 



These cursory examinations a[)pear to suggest tliat the structural causes 

 of color in spiders are probably the following : First, color stains diffused 

 througliout the tissues ; second, pigment granules of various hues 

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

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

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

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

 of the Lepidoptera ; 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 which 

 they are grouped and overlaid in order to 

 form tlie various color spots and pattern 

 outlines produced exclusively or in part by 

 them. The subject might well repay the 

 careful study of the microscopist, and it 

 may often be found tliat 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 Drassidas 

 and Agalenidse 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. 

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

 cence of the abdomen, which 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. 



Fig. 310. Fig. 3U. 



Fig. 312. Fig. 313. 



Micaria longipes. 

 Figs. 310 and 313. Wliite scales from spots 

 on abdomen. Fig. 311. Scale from hind- 

 er half of abdomen. Fig. 312. Scale from 

 fVont of abdomen. (After Emerton.) 



Color 



Scales. 



' In a letter to the author. 

 •"• Id., plate iii., Fig. 1. 



* See New Eng. Drassidse, plate iii., Fig. 3, e. 



