COLOR AND THE COLOR SENSE. 349 



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

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

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

 the segments. 



The ccphalothorax 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- diaracter, the entire fore part of the body having tlie hardness 



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



and Legs. ° 



domen, on the contrary, is enclosed ni 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 s])ecimens of spiders. On 

 the cejihalothorax there are often several longitudinal bands, one on eacli 

 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. ccphalothorax, 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 blacki.sh. 



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. 

 ?'^ ^ _ Among these are Argyroepeira hortorum, Argiope argyraspis, Ar- 



giope cophinaria, Argiope argenteola, Epeira insularis, Ga.stera- 

 cantlia cancer, and Phidippus morsitans. ' 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 tlie path suggested, 

 and reach positive determinations. 



The metallic white upon the ccphalothorax of Argiope argyraspis is 

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



clo.sely one upon another and reflect white light, the combined 

 e a ic i-edections forming the metallic a}q)earance of tlie 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 ccphalothorax. The black transverse bands on the ab- 

 domen are produced by amorjihous granules of black pigment just beneath 

 the skin, which thin out towards the margin of the band, becoming j'cllow 

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

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

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



' I luiil purposed to include in this volume a plate of colored drawings representing, in 

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

 compelled the postponement of this plate to tlic tliird volume. 



