COLOR AND THK COLOR SENSI). 327 



legs and cephalothorax having brownish rings and bands, and the abdo- 

 men being a lighter yellow with brownish spots. 



Thus the colors run, with ^varieties of tints and hues that confound 

 the observer. Most of these spiders appear to be of one age and at the 

 same period of gestation. Those that are least advanced, perhaps, may be 

 said to have the white colors. The next degree of maturity in mother- 

 hood shows the yellow tints. The next the deepening brown, and so as 

 the creature ages the colors seem to deepen and brighten. When the last 

 stage of maturity has been reached, and the spider mother has spun her 

 beautiful silken cocoon, depositing therein her eggs neatly and securely 

 blanketed against assaulting enemies and winter frosts, these colors will 

 gradually merge into the dull, dark hues of the sere and yellow leaf of 

 which her nest is built, and so her life will fade away. 



The physiological causes of this change in the colors of Trifolium 

 present an interesting study. Other species known to me are subject to 

 changes. In some the change is quite marked. In some there is a great 

 variety of coloring, and particularly of dorsal patterns, as in the case of 

 Epeira patagiata and Epeira parvula, but the Shamrock spider exceeds all 

 species which I have ever observed in the puzzling variety and contrasts, 

 as well as beauty, of the colors it assumes in the closing weeks of its life. 



II. 



The color of young spiders is almost without exception light yellow or 

 givi-n, whitish or livid, tints that blend well with the prevailing greens of 

 foliage and young twigs, and the grays of bark on trees, of rocks 

 Color De- an j so ^ rpj^g j g pro^^ly c l ue largely to the fact that the tis- 

 8 ^~. sues are at that time translucent. The effect may also be caused 

 Young. kv the absence of acquired food in the alimentary tract and lack 

 of distribution throughout the system of other than the prena- 

 tal nutriment. 



As young spiders advance in age the color deepens, which is caused, no 

 doubt, by gradual hardening of the tissues, thus making them more opaque. 

 Up to this period no food has been taken, hence the absence of food alone 

 is not sufficient to account for the lighter colors of the first stages after 

 exode. Yellows and browns in various tints occur at this period, and 

 in some cases though not generally, I believe color patterns which are 

 characteristic of the various species in adult life begin to appear with 

 more or less distinctness, or at least suggestively. It is not until Seden- 

 tary spiderlings have established themselves upon their own webs, and, so 

 to speak, have set up housekeeping for themselves, that the characteristic 

 colors and markings of the species begin to appear with positive degrees of 

 distinctness. 



The Attidse, like birds, moult frequently, and at each moult the mark- 

 ings may change, so that some of the older writers have formed several 



