94 Journal New York Entomological Society. [Vol. xm. 



on or among the yellow flowers ; an occasional white one occurring 

 which may have been a recent arrival from some bush or other plant. 

 This is an exact parallel with the instance observed by Mr. Banks, 

 when the spiders occurring early in the spring in Virginia on the 

 white tri Ilium, afterwards become yellow on the yellow flowers of the 

 dog-tooth violet, there being no white flowers in the neighborhood. 



3. By enclosing a couple in a bag tied over a golden rod they 

 have actually been found to change from white to yellow in the course 

 of ten or eleven days. 



4. There is an actual change in color, and the assembling of yel- 

 low spiders on yellow flowers is not a case of color-preference, but of 

 a gradual alteration in the color of the pigment of the integument. 

 Whether as in the case of lepidoptera, the change takes place at or 

 directly after the time of molting has yet to be ascertained. I have 

 no observations directly bearing on this question. 



5. In rare cases (3) white M. vatia were collected on the white 

 Solidago bicolor. 



6. No M. vatia or any other species of Thomisidse were found on 

 blue or white asters or on life everlasting, of which hundreds were 

 examined. 



7. The result of the coloring, while in harmony with the color en- 

 vironment, is certainly not to protect the spider from the attacks of 

 birds, as the only kind of spider-eating bird is the humming bird, 

 other kinds of birds, as investigation shows, not feeding on spiders. 

 On the other hand, the coloration is so far cryptic that flies and other 

 prey of the spider less easily observe its presence. This, however, is 

 quite a subsidiary matter ; without reference, so to speak, to the 

 biological environment, the main fact is that the color of the spider is 

 the mechanical result of exposure to an environment of this or that 

 color. 



8. The cause of the change of color is simply the action of light, 

 and in the case, for example, of yellow individuals, to the reflection 

 of yellow light from yellow flowers continued for a period of exposure 

 varying from several days (three or four) to one or more weeks. 

 There are multitudes of similar cases in other groups of animals, and 

 protective coloration so-called is simply the mechanical result of the 

 operation of a primary physical agent, /'. e., light. 



The colorational change is not due to natural selection or to the sur- 

 vival of some one or even several fittest individuals, since hundreds 



