36 
BULLETIN 100, U. S. DEPARTMENT OF AGRICULTURE. 
Spiders. 
The commonest spider predaceous on walnut plant lice is T7ie- 
ridium placens Keyserling. This spider may be found on the trees 
during the months of August and September and has a habit 
of curling around itself the edge of the leaf under the protec- 
tion of which to deposit its egg sac. This species was determined 
by Mr. Nathan Banks, of the Bureau of Entomology, who says of it 
"* * * a species found on the Pacific coast. They do not 
choose their food, but from location of web are apt to get many 
plant lice." This and other spiders are of comparatively small 
economic importance in the control of aphides. 
Camptobrochis brevis Uhler. 
Camptobrochis brevis Uhler, which was determined by Mr. Otto 
Heidemann, of the Bureau of Entomology, is a small black capsid, 
measuring hi the adult stage 4.2 by 1.9 mm. Its larva is white, with 
conspicuous black markings. Both immature and mature individ- 
uals were observed actively and abundantly attacking plant lice 
during August, 1912. They do not occur in numbers earlier in the 
year and disappear in September. Thus their beneficial work is 
limited. 
Leucopis sp. 
A fly of the family Agromyzidae, Leucopis sp., in its larval state 
preys upon walnut plant lice from June to August. The small 
yellow maggots superficially resemble syrphid larvae. They are 
never very abundant and are not a great factor in the control of the 
"lice." The life cycle in summer is completed in 24 days or less 
and there are several broods in California. 
Chrysopid or Lacewing Flies. 
Of scarcely less importance economically than the ladybird beetles 
and syrphid maggots are the active reddish-brown larvae of the " lace- 
wings." Chrysopa majescula Banks and 0. calif ornica Coq. are two 
species of economic importance in California. Table X shows the 
predatory activities of two larvae of the latter species in the fall of 
1912. The aphides consumed by these larvae were of all sizes and 
averaged about 1.5 by 0.5 mm. 
Table X. — Chrysopa californica: Predatory activities on walnut -plant lice, Wahmt 
Creek, Cal, 1912. 
Larva 
No. 
Date of— 
Number 
"lice" 
eaten to 
molt 1. 
Date of 
molt 2. 
Number 
"lice" 
eaten, 
molt 1 to 
molt 2. 
Date of 
spinning 
cocoon. 
Number 
"lice" 
eaten 
from 
molt 2 
to pupa- 
tion. 
Total 
"lice" 
eaten. 
Num- 
ber 
days 
feed- 
ing. 
Hatch- 
ing. 
Molt 1. 
1 
2 
Sept. 18 
18 
Sept. 22 
21 
11 
22 
Sept. 27 
26 
70 
57 
Oct. 8 
265 
300 
346 
379 
20 
19 
