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



abdomen above and beneath, and also the legs. This is the*first yel- 

 low one I have seen for some years. The yellow hue is uniform, 

 though the abdomen was a little deeper in hue than the rest of the 

 body. 



Two days later (August 6) the yellow ones had greatly increased 

 in number with the blossoming of additional plants of the Solidago i 

 for now ten yellow ones were found to one on the 4th. 



The spiders were thoroughly well protected from observation, both 

 by their pale yellow color, and by their habit of hiding among the 

 greenish yellow calices of the flowers, not resting as a rule on top of 

 flowers. 



Was the change of color due to alteration of the pigment, or to 

 color-preference ? Had the yellow ones simply gathered on the newly 

 opened golden rod and come from the yellow flowers? Evidently 

 not, because there were no other abundant yellow flowers, the buttercup 

 having mostly gone out of blossom, and the only other flowers on 

 which they had been detected were the fleabane, ox-eye daisy, and 

 wild rose, these being the commonest flowers at Merepoint. 



During the latter part of August yellow ones prevailed on the 

 golden rod. On the 12th I found three rather large yellow M. vatia 

 on the golden rod, one large one striped on the side of the cephal- 

 othorax and abdomen. Only the young ones were whitish. It seems 

 quite apparent that the yellow ones have more or less gradually changed, 

 since they are not of the exact shade of yellow, the hues differing in 

 intensity as if they had gradually become adapted to the change of 

 color, and they are all yellow with a shade or tinge of green so that 

 they are more in harmony with the general greenish yellow of the 

 heads of the flowers among which they hide ; as they are not, at first at 

 least, of a uniform deep straw-yellow it is evidently a case of gradual 

 adaptation, and not simple color preference, which assumes that the 

 spiders were originally yellow and migrated to the Solidago from some 

 other plants. 



August 15 I found two small white ones on the golden rod and 

 three or four yellow ones, and through the month middle and large- 

 sized yellow ones occurred, with young colorless or whitish ones. 



That they do change in consequence of adaptation to the yellow 

 of the golden rod seems quite satisfactory demonstrated by my 

 beating from the golden rod, eighteen M. vatia into the umbrella, 

 all of which were distinctly yellow, besides an additional small whit- 

 ish one. 



