348 



AMERICAN SPIDERS AND THEIR Sl'INNINGWORK. 



majority of British cocoons are white ; green or greenish, yellow, and yellow 

 brown being the other colors represented. These colors are distributed 

 quite indifferently of the maternal colors. 



The color of the silk extruded from the spinnerets of spiders of all 



tribes in the construction of snares is, with few exceptions, white, some- 



times having a steel blue tint, and often a lustre which gives it 



the appearance of spun glass. There are some exceptions to this 



rule, as, for example, the round web of Nephila is uniformly 



woven with yellow silk ; and perhaps a wider study of the spinningwork 



of araneads will show that there are other exceptions, and perhaps many 



of them. 



The differences of color in the spinning silk of araneads appear in the 

 construction of the cocoon. Many cocoons are composed of white silk, per- 

 haps it may be said the majority of them, but others again show some 

 pretty varieties of color, and in some species several hues of silk will be 

 used in weaving one cocoon. 1 



Among Orbweavers the colors used in cocooning are principally white ; 

 but one frequently finds yellow in various shades, green, and sometimes 

 brown. A few Lineweavers make colored cocoons, and among Tubeweavers 

 may be found a few species whose cocoons are various shades of red, some- 

 times quite bright. I often find these cocoons in the shape of little plates, 

 with the convexity upward, attached to bark and stones, and showing a 

 very dainty appearance, but have not been able to fully identify them with 

 the species making them. 



An examination of the spinning glands of spiders under the micro- 

 scope will show, in some species at least, as Argiope cophinaria, several 

 colors represented in the liquid contents. The causes controlling the secre- 

 tion of these specially colored silks are, of course, physiological, but one 

 cannot presume to guess even what they may be. 



VIII. 



The forms in which the coloring materials are arranged constitute the 

 various patterns or marks that characterize spider species. These patterns 

 are most varied and prominent upon the dorsum of the abdo- 

 men, although the venter and the sternum are also sometimes 

 highly colored. While there is much variety in the arrangement 

 of these patterns, there is, on the whole, a general tendency to form a 

 folium or leaf shaped outline, scalloped on the outer margin. This folium 

 outline appears to have some orderly relation to the little pits or points of 

 muscular attachment, and, in a general way, may be said to be regulated 

 by those sections of the abdomen which have commonly been held to 



1 See Chapter IV., page 80, and Plate IV., Figs. 3, 4, 5. 



