34 
BULLETIN 100, U. S. DEPARTMENT OF AGRICULTURE. 
K 
\®-\ 
sm 
j%. 
Fig. 
1>, 
18.— a, Monellia caryx, antenna of male; 
Monellia caryella, two views of right an- 
tenna of male. ( Original .) 
occurs a large black spot on the pleurae. 
Abdomen unarmed, pale green or green- 
ish yellow; segments 1 to 8, inclusive, 
with two dusky brown oval spots on 
each. Cornicles pale, concolorous with 
the body, very small, considerably 
broader than long. Cauda concolorous 
with the abdomen, globular. Abdomen 
about as long as head and thorax com- 
bined, not wider than the thorax. 
Beak pale, barely reaching second 
coxse. Sternum and underside of the 
eighth abdominal segment black. 
Measurements: Length of body, 1.57 
mm.; width of body, 0.62 mm.;' ex- 
panse of wings, 4.62 mm.; antenna, 
joint I, 0.080 mm.; joint II, 0.041 mm.; 
joint III, 0.412 mm.; joint IV, 0.317 
mm.; joint V, 0.260 mm.; joint VI, 
0.175 mm.; filament, 0.108 mm.; cauda, 
0.067 mm.; cornicles, 0.009 mm. 
Described from three speci- 
mens, Walnut Creek, Cal., 1912 
and 1913. 
MONELLIA CALIFORNICA Essig. 
Monellia californicus Essig, Pomona 
Jour. Ent.,v. 4, no. 3, p. 767, Nov., 
1912. 
In southern California feeding 
on the underside of the leaves of 
the California black walnut 
(Juglans californica) there has 
recently been found a plant- 
louse closely allied to Monellia 
caryse and M. caryella. The 
writer has never seen this aphis 
in nature, but has received speci- 
mens from Mr. Essig, who de- 
scribed it. 
KEY TO THE SPECIES OF MONEL- 
LIA KNOWN TO OCCUR IN CALI- 
FORNIA. 
The following key will serve 
to distinguish the four species 
of walnut aphides occurring in 
California. 
