66 
BULLETIN 903, IT. S. DEPARTMENT OF AGRICULTURE. 
Table XVI gives measurements for four individuals of the second- 
instar radicicole. 
Table XVI. — Measurements of second-instar radicicoles 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. 
0.419 
.448 
.439 
.499 
Mm. 
0.234 
Mm. 
0.154 
Mm. 
0. 0625 
.0624 
Mm. 
0. 0526 
.0518 
Mm. 
0. 0190 
.0205 
Mm. 
0.0204 
.0205 
Mm. 
0. 0586 
.0589 
Mm. 
2 
3 
.257 
.270 
1.113 
.168 
4 
0. 0171 
i Telescoped. 
The roughened tubercular areas on the dorsal surface are more 
conspicuous after the first molt, and a rapid increase in bulk is 
apparent during the second instar. 
The second, third, and fourth molts occur at practically equidistant 
periods. Under highest temperatures and optimum food conditions, 
these instars are passed in about two days apiece. Under a tempera- 
ture of 58° F. from three to eight days elapse between molts, the 
average being about five and one-half days. 
Table XVII gives the measurements of five individuals of the 
third instar. 
Table XVII. — Measurements of tliird-instar radicicoles of the grape phylloxera, 
Walnut Creek, Calif. 
Individual No. 1 
Length 
ofbody. 
Maxi- 
mum 
width 
ofbody. 
Length 
of beak. 
Length 
of hind 
femur. 
Length 
of hind 
tibia. 
Length of antennal joints. 
Length 
of sen- 
sorium. 
1 
2 
3 
1.. 
Mm. 
0.592 
.524 
.522 
.649 
Mm. 
0.303 
.312 
.332 
.355 
Mm. 
0.178 
.164 
.179 
.155 
Mm. 
0. 0699 
Mm. 
0. 0607 
Mm. 
0. 0202 
.0252 
Mm. 
0. 0321 
.0207 
Mm. 
0.0616 
.0568 
Mm. 
0.0 
2 
.0144 
3 
.0739 
.0732 
.0758 
.0741 
.0622 
.0687 
.0660 
.0692 
4 
.0241 
.0197 
.0206 
.0205 
.0187 
.0194 
.0634 
.0589 
.0598 
.0177 
5 
.648 
.371 
.145 
.0186 
6 
.0190 
1 
1 Individuals 1-3, newly molted; 4, two days after molt; 5, three days after molt. 
During the third instar (PL X, a, &, c) the increase in bulk con- 
tinues rapidly. The dorsal tubercular areas are larger than in the 
previous instar, but in color and shape no differences appear. 
Table XVIII indicates the measurements of seven individuals of 
the fourth (penultimate) instar. 
