350 AMERICAN SPIDKKS AND THEIR SPINNINGWORK. 



In Argiope cophinaria the metallic color of the cephalothorax is pro- 

 duced by hairs in the same way as with Argyraspis. These hairs are 

 wavy ; there appear to be two kinds, one flattened, with a wavy 

 outline, having somewhat the appearance of cotton fibre, which 

 may, however, be produced by irregular cavities or spaces within the 

 hairs. Others again, present a similar appearance, but are cylindrical. 

 On the abdomen of Cophinaria the colors are produced chiefl}' by pig- 

 ment granules beneath the eiDiderm, the chitinous layers of which are 

 arranged in beautiful undulating lines. 



The pretty orange color upon tlie thigh of Epeira insularis is pro- 

 duced chiefly by vast numbers of pigment granules lying beneath the 

 epiderm, the secreted layers of which are arranged in diamond shaped 

 figures. 



Argyroepeira hortorum, the most beautifully colored of our indigenous 

 spiders, makes a fine object for mounting in order to show colors. The 

 hairs have little or nothing to do in producing these varied 

 ^^^ hues, which are due to green and yellow pigment granules, and 



„ . , to what appear to be chromatophores. These chromatophores are 



white for the most part, though some of them are yellow tinted, 

 and they yield a strong white reflection, which, it seems to me, is a chief 

 agent in producing the brilliant silvery white of this aranead. 



In the case of Phidippus morsitans the color of the abdomen is due 

 to several causes. The black shades with dark green metallic reflection 

 on the sides are produced chiefly by dark green pigment granules under- 

 neath the skin, and in part by black hairs. The white spots on the sides 

 of the dorsum are composed of peculiar white lanceolate hairs laid one 

 upon another. They are marked by longitudinal striations on the surface, 

 which give it, under the lens, the appearance of a minute ear of Indian 

 corn. The little yellow lunettes of color on the dorsum near the apex 

 appear to be composed of somewhat similar hairs, of nearly the same 

 shape, but a little more elongated, j^ellow in color, and these, instead of 

 longitudinal grooves, have slight feather like projections or papilke irregu- 

 larly distributed over tlie surface.' 



The remarkable metallic green on the mandibles of this species is pro- 

 duced by a method quite different from any of those above named. The 

 surface of the mandibles is broken up into a number of rugosities, ar- 

 ranged, though somewhat irregularly, in arcs of circles. These ridges 

 appear to act as prisms, refracting the liglit ; and to this evidently is due 

 the brilliant metallic color wliich has attracted the attention of all observ- 

 ers of the species. Under a microscope the minute lunettes and waves of 

 green light are readily distinguished; l)ut the natural eye does not separate 



' These hairs in the color patches on the a))domen of P. morsitans appear to he of the 



tyjie iif Mr. Wagnrr's dubshaped hairs. (Fig. 207.) 



