ill' Journal New York Entomological Society. [Vol. xin. 



been long enough exposed to the reflections of the roseate petals of 

 this flower. 



Beddard (Animal Coloration, p. 113) suggests that the yellow 

 color of the Thomisus onustus is "not adaptation but simply due to 

 age." It once occurred to me that this might be the case, but I think 

 that the facts I have stated are more strongly in favor of a slow adap- 

 tive change, and it is disproved by the fact that old, fully grown white 

 examples frequently occur throughout the last of the summer season. 



Mr. Cook,* referring to what was probably Misumena vatia, quotes 

 from an article by L. C. Palmer, "an intelligent observer, but not a 

 naturalist," to the effect that he found a species of spider near Phila- 

 delphia which was purple on the purple boneset, pure white on the 

 white panicle of the boneset proper, while on the golden rods it was 

 yellow. 



In Italy Pavesi " finds that this same species when living on flowers 

 is white, or white and yellow with red stripes on the abdomen ; but 

 that when found among the grass it is grass-green, with dark, obscure 

 stripes on the cephalothorax and palpi." (Quoted by Mrs. Peckham, 

 1. c, p. 88.) 



Mr. Emerton f found M. asperata perched on a flower of sorrel 

 ( Rumex acetosella), its colors being exactly those of the flowers. In 

 " The Common Spiders of the United States " (1902) he states that the 

 Misumenas live on plants, among the flowers, especially on large flat 

 clusters like those of carrot and thoroughwort. " Whether," he says, 

 " spiders prefer flowers colored like themselves is an unsettled ques- 

 tion ; at any rate Misumenas of all colors and both sexes have been 

 found in white flowers. Occasionally individuals are found on flowers 

 of exactly the same color as themselves ; for example, deep yellow M. 

 aleatoria on the wild indigo Baptisia tinctoria, and the reddish M. as- 

 perata on the flowers of sorrel." 



The probable cause of the change of color. — The change of color 

 in the flower spiders appears to be due primarily to the direct action 

 of the sun's light, and secondarily to the absorption of the color 

 light-rays by the pigment of the integument. That it is obviously in 

 no way the result of the food is evident, because these spiders feed upon 

 the colorless blood of insects. We know nothing of the immediate 

 cause of such changes, which occur during the life-time of the indi- 



* American spiders and their spinning work, II, p. 36S, 1890. 



f Spiders of the family Thomisidce, Trans. Conn. Acad., VIII, 1S92, p. 370. 



