10 
THE EED SPIDEE OX HOPS IN CALIFORNIA. 
An extract from a letter from a former hop grower in Washington 
State describes conditions there as follows: "The 'red spider' was 
here in 1901, but did little damage. It gradually increased until 1905, 
when we let 25 of 85 acres blow away and what we did bale was 
trash. Then we gave up the fight." 
The red spider is reported to have been very destructive to hops 
at Agassiz, British Columbia, but for the past few years has not ap- 
peared in injurious numbers. 
The past seasons were very late, and the mites were not present in 
noticeable numbers in the hop fields near Sacramento until the middle 
of June. Even so, they had done much damage by August, 1911, 
and if the crop had not been promptly and rapidly picked many of the 
hops would have " blown away/' 
resulting in the total loss of a 
great portion of the crop. 
LIFE HISTORY. 
THE EGG. 
Description . — T he eggs of 
Tetranychus bimaculatus (fig. 1) 
are small, spherical, pearl-like 
objects, about one-sLxth of a 
millimeter in diameter, though 
somewhat variable in size. 
From 10 to 450 are usually present on a leaf, and with the aid of a 
hand lens they are readily found upon infested foliage. 
Where laid. — The eggs are deposited singly and are promiscuously 
distributed among the webs and upon the underside of the leaves. 
They are not attached to the host plant by protecting webs, as are 
the eggs of the citrus "red spider" {Tetranychus mytilaspidis Riley), 
but are held by strong filaments with which they chance to come in 
contact. Many eggs have been observed on the loose web which is 
ordinarily spun over infested leaves. 
Incubation. — The incubation period varies according to temperature 
and general climatic conditions. In the experiments conducted at 
Berkeley, Cal., during February, 1912, the incubation period was 
found to be from 8 to 10 days. This period during May was from 5 
to 10 days, with an average of 7.2 days, while in July, 1911, and during 
some very warm weather in 1912 it was only 44 days. The relatively 
higher temperatures of the summer are responsible for this shortening. 
Fig. 1.— The red spider ( Tetranychus bimaculatus): Egg 
(position indicated by white circle) among webs on 
surface of leaves. Greatly enlarged. (Original.) 
