COLOR AND THE COLOR SENSE. 349 



indicate a segmentation. In other words, some writers are disposed to con- 

 sider the abdomen as segmented, and, in a rough way, the symmetrical 

 divisions in the pattern folium may be said to outline the articulations of 

 the segments. 



The cephalothorax is most frequently uniform in its color, commonly 



with longitudinal stripes of different shade. It follows, in a general way, 



the coloration of the legs, which it resembles in its chitinous 



Cephalo- character, the entire fore part of the body having the hardness 



4-T-* f\TQ V 



, T which is characteristic of the enclosing walls of insects. The ab- 

 domen, on the contrary, is enclosed in a soft skin, a fact which 

 exposes it to injury, and causes its rapid decay after death, one of the 

 principal difficulties in the way of preserving specimens of spiders. On 

 the cephalothorax there are often several longitudinal bands, one on each 

 side, near and indeed quite surrounding the margin, and two drawn from 

 the suture of the caput backward. There is also frequently a band of 

 color in the median line from the middle of the eye space backward. The 

 legs are usually colored like the cephalothorax, and are generally uniform 

 in hue, except that at the joints there are rings of color usually darker 

 than the rest of the leg. The feet are nearly always black or blackish. 



In order to determine if possible the structural causes producing color 



in spiders, I made studies from a number of dissections of various species 



chosen with special regard to variety and brilliancy of colors. 



fp S ^ s Among these are Argyroepeira hortorum, Argiope argyraspis, Ar- 



giope cophinaria, Argiope argenteola, Epeira insularis, Gastera- 



cantha cancer, and Phidippus morsitans. 1 I do not speak of the results 



positively, for the studies are in a field where trained histologists alone 



are competent to decide. But I venture to give some indications of what 



appeared to me, in the hope that others may follow the path suggested, 



and reach positive determinations. 



The metallic white upon the cephalothorax of Argiope argyraspis is 

 produced chiefly by a vast number of white hairs. These are packed 

 closely one upon another and reflect white light, the combined 

 __ e c reflections forming the metallic appearance of the object. The 



metallic hues of the abdomen of Argyraspis are produced in 

 part by closely thatched white hairs that reflect white light in the manner 

 of those upon the cephalothorax. The black transverse bands on the ab- 

 domen are produced by amorphous granules of black pigment just beneath 

 the skin, which thin out towards the margin of the band, becoming yellow 

 as they diminish. There appears also to be a diffused yellow stain in the 

 chitine, and, in addition, white pigment bodies which resemble the chro- 

 matophores that give the color in frogs and lizards, for example. 



1 I had purposed to include in this volume a plate of colored drawings representing, in 

 a general way, the indications of these studies, but sundry disappointments and delays have 

 compelled the postponement of this plate to the third volume. 



