14 BULLETIX 416^ U. S. DEPARTMENT OF AGRICULTURE. 



of numerous synonyms by early writers. For a long time it was 

 held that this diversity in color was due mainly to the varying natine 

 of the host plants. 



Ewing (1914) conducted a series of experiments for the purpose of 

 ascertaining the nature, situation, and composition of what he styles 

 the six principal pigments of the common red spider, namely, green, 

 yellow, orange, carmine, black, and brown. In summarizing he states 

 that the green color is due to the presence of chlorophyll in the blood 

 or tissues of the mites; that the yellow color arises from a pigment 

 derived from and closely alhed to the chlorophyll green pigment and 

 which is elaborated from the green pigment ; that the orange color is 

 due to a pigment of that color which is dissolved in the cell fluids or 

 the blood and is quite permanent, is unaffected by age, and is never 

 found except in adults on certain hosts; that the blackish color does 

 not arise from a distinct pigment, but is due to the concentration of 

 the yellow pigment in the food material; that the brown color also 

 is due to a superabundance of the yellow pigment; and, finally, that 

 the carmine of the region of the eyes is due to the presence of a per- 

 manent pigment which is present even before hatching. Ewing 

 states that in his experience reddish individuals are exceptional. 

 The experiments conducted by Ewing are a distinct step in advance 

 and, it is hoped, will stimulate additional research in that direction. 

 Perkins was of the opinion that dark-colored females are ones that 

 have been impregnated, and that light-colored females are weak sex- 

 ually and have either no offspring or impotent progeny. 



As a rule the females we have observed are either brick-red, orange, 

 amber-yellow, greenish, or brownish-green. During the period from 

 April to September, inclusive, the vast majority of adult females in 

 the South are a conspicuous brick-red color. Toward late fall the 

 females often assume a salmon-yellow color in the Southeast. Von 

 Hanstein (1902) also found this to be the case in Europe with T. 

 althaea, and he considered that the color was associated with prepara- 

 tion for wintering. It certainly is very striking that the red type of 

 female almost disappears in the fall and is replaced by the orange- 



yeUow type. 



Description of Male. 



The color of the male is rusty salmon; the lateral spots are less 

 conspicuous and usually located near the front of the abdomen ; the 

 cephalothorax is often nearly clear straw color. Eyes crimson, rela- 

 tively more conspicuous than in the female. The legs I are usually of 

 a deep salmon color (this not being the case with the female) . Body 

 cuneate-ovate, widest at the anterior region of the abdomen, the 

 cephalothorax rounded in front, abdomen tapering to an acute point 

 posteriorly; bristles arranged very similarly to those of the female, but 



