74 
BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 
eyes show their red pigment and soon become prominent. Legs and 
antennae are relatively long, and the femora exceed the tibiae in 
length. At all times the rows of tubercular areas on the dorsum are 
well marked. During the nymphal instar the insect shows a very 
considerable growth: the newly molted individuals are quite flat, 
but full-grown nymphs are roughly cylindrical. 
DESCRIPTION OF STAGES. 
The nymph or pupa, full grown. 
PI. XI ; test fig. 9, p. 85. 
General color orange or orange yellow; anterior part of rnesothorax and 
inesosternum whitish, or at least always noticeably paler than the rest of body. 
Antennae pale yellow, extended but little beyond anterior margin of prothorax. 
Compound eyes and ocelli dark red ; former composed of large number of facets. 
Head and abdomen bearing 4, thorax C longitudinal rows of dark tubercular 
areas (coarse roughening of epidermis), each surmounted by a spine; wing pads 
dark gray, grayish black, or rarely jet black; legs pale yellow, often with a 
dusky cast ; abdomen with 7 visible segments, rnesothorax apparently bisected by 
a transverse fold ; beak very pale yellow, reaching to posterior coxse. 
Measurements of 6 individuals are given in Table XXV. 
Table XXV. — Measuremem 
of nymph of the grape phylloxera. Walnut 
Creek, Calif. 
Individual No. ' 
Length 
of body. 
Maxi- 
mum 
width 
of body. 
Length 
of beak. 
Length 
of hind 
femur. 
Length 
of hind 
tibia. 
Length of antennal joints. 
Length 
of sen- 
sorium. 
1 
2 
3 
1 
Mm. 
1.102 
Mm. 
J/77?. 
0. 3295 
Mm. 
0.1500 
.1464 
.1419 
.1438 
.1089 
Mm. 
0. 1366 
.1384 
.1321 
.1304 
.1071 
Mm. 
Mm. 
0. 0402 
.0350 
.0331 
.0332 
.0339 
.0295 
Mm. 
0.1536 
.1545 
.1455 
.1455 
.1179 
.1184 
Mm. 
0. 0223 
0. 0339 
.0224 
2 
.889 
.3600 
.0230 
.0254 
3 
.957 
.507 
.3339 
.0321 
,0304 
.0223 
.0232 
4 
.851 
.798 
.725 
1.121 
1.197 
5 
.511 
.2695 
.13S9 
.1252 
.0315 
.0309 
.1577 
.0198 
6 .♦. 
7 
.558 
-.569 
8 
1 Individuals 1,7, and 8 at end of stage; 4, 5, and 6 at beginning of stage; 2 and 3 about middle of stage 
Newly molted nymphs average about 0.78 mm. in length and ma- 
ture nymphs about 1.1 mm. The nymphs are always more active 
than the immature wingless forms, wandering larvae excepted. Their 
eyes are well developed, as in the winged insect, and they have the 
ocelli found in that form. The third joint of the antennae bears a 
single sensorium corresponding to the apical one of the migrant, and 
as the last molt approaches the migrant antennae show through the 
nymphal skin, and thus the nymphal antennae appear to bear two 
sensoria. 
