14 BULLETIN 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 nature 
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. Insummarizing 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 allied 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 mm 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- 
yellow 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 
