12 
THE EED SPIDER OX HOPS IN CALIFORNIA. 
THE ADULT. 
Description. — The adults of Tetranyclius bimaculatus (figs. 3, 4) 
are small, greenish yellow or, in some eases, reddish mites ranging 
in size from 0.27 mm. in the male 
to 0.50 mm. in the female. The 
abdomen joins the cephalothorax, 
formed by the fusion of the head 
and thorax, at its full width and 
extends over the portion to 
which the posterior pair of legs 
is attached. The abdomen, the 
cephalothorax, and particularly 
the appendages are well provided 
with hairs. 
The two sexes are very distinct. 
The female is much the larger and 
has a broad, rounded abdomen, 
while in the male the abdomen is 
narrow and tapering. These dif- 
ferences are so well marked that 
the sexes may be distinguished 
under an ordinary hand lens. 
Fig. 3.— The red spider: Adult female, dorsal view. 
Greatly enlarged . (Original.) 
Copulation. — Copulation begins as 
soon as the mites become adult, the 
female often receiving several males. 
Contrary to the usual method, how- 
ever, the male operates from beneath 
the female. The male mite forces its 
way under the abdomen of the female, 
braces its legs against the leaf, and 
directs the genitalia over its back. 
Parthenogenesis. — The idea that par- 
thenogenesis occurs with the red 
spider is an old one, and during this 
investigation a few experiments were 
carried on along this line. A morn- 
ing-glory (Ipomcea sp.) was cleaned 
of all mites and eggs, the petioles 
of the leaves were banded with tree 
tanglefoot, and adult mites were placed upon 10 of the leaves. After 
eggs were observed the female and all but one of the eggs were 
Fig. 4.— The red spider: Adult male, dorsal 
view. Greatly enlarged. (Original.) 
