2 
of threads is frequently so dense as to form a tissue plainly visible at 
a little distance. Webs are constructed upon the lower side of leaves, 
and attached here and there to projecting hairs, veins, or the edges of 
the leaves. Within the webs thus formed the mites feed in their 
different stages, and the eggs are laid from which the young develop. 
DESCRIPTIVE. 
The, general appearance of this red spider as seen under a micro- 
scope is well shown in figure 1, a. At ) a greatly enlarged palpus of 
the same species is illustrated, and c shows the claws, similarly 
enlarged. 
The length of full-grown individuals, including the palpus, is about 
A; inch (0.4 to 0.6 ™™), and the width about 7 $5 inch (0.25 to 0.80 ™™), 
the thickness being 0.17 to.0.20™". The form is broadly oval, the 
width greatest in the anterior third of 
the body, back of the eyes, where the 
sides are somewhat distended. The 
general color of the adult is reddish, 
usually more or less tinged with yel- 
Z lowish or orange, and most specimens 
have a dark spot on each side, due to 
the. food contents of the body, from 
which the scientific name bimaculatus 
(two-spotted) has been derived. 
Careful study of different individ- 
uals as they occur on garden vegetables 
and on horticultural and other plants 
erowing in the field with those taken 
Fic. 1.—The common red spider jy greenhouses shows no appreciable 
(Tetranychus bimaculatus): 4a, Sieh : ; = 
cane b) palpuse te uclaws. ay- Gliberences: According to Mr. Nathan 
ee es more Banks, specimens taken in Florida on 
Ries ie Datura and at Washington, D. C., on 
violets are red, while those from Orono, Maine, and those from the 
District of Columbia on squash and peach, and on rose from Idaho, 
are greenish with more or less dark markings. 
The eggs are extremely minute, spherical, of variable diameter, 
glassy, and are scattered and loosely attached about the webs. 
The young are somewhat similar in appearance to the adults, but 
differ in having only three pairs of legs, while the adult has four 
pairs. ; 
DISTRIBUTION. 
This red spider is well distributed throughout the eastern United 
States, and was identified as occurring as far west as Idaho in 1900. 
In 1902 it was recognized from Brighton, Wash.; in 1907 from south- 
[Cir. 104] 
