422 
Journal of Agricultural Research 
Vol, XXVI, No. 9 
vicinity of Sandusky, Ohio, oviposition probably began during the 
first week in June. 
The nymphs. —The nymphal period is passed on the under surface of 
the grape leaves, the young feeding in the same manner as the adults by 
sucking juice from the leaf cells. The young move about but little dur¬ 
ing the developmental period, remaining for the most part on the leaves 
on which they were hatched. In common with Erythroneura comes , the 
three-banded hopper passes through five nymphal instars, as shown in 
the accompanying figures. (PI. 2, A-E.) 
Nymphal period of first brood. —The average length of the nymphal 
instars for first-brood individuals in 1922 follows: First instar, 3.8;sec¬ 
ond, 3.0; third, 3.4; fourth, 4.4; fifth, 5.4 days, with an average total of 
20 days (average mean daily temperature, 72.8° F.; maximum nymphal 
period, 22 days, minimum, 17 days). As the nymphs migrate very little 
from leaf to leaf, it is possible to rear them on unprotected growing grape 
leaves in the insectary, merely wrapping the petioles with absorbent cotton 
to protect against spiders and contamination. This avoids an abnormal 
humidity, a factor that has not always been eliminated in previous work. 
Appearance of adults in summer. —-The appearance of first-brood 
adults in vineyards is determined by the presence of mating pairs. 
The first pair was found on July 2, and the last on August 31, in 1922, 
although it can not be stated positively that the last ones were not of 
the second brood, since the existence of a third brood is still an open 
question. Mating pairs are most frequent in early morning. 
Period of incubation of second brood. —The incubation period of 
second-brood eggs, laid between July 26 and 31, 1922, averaged 14.7 
days, or one day longer than the earlier generation. The average mean 
daily temperature of 71.4 0 F. as compared with 73.9 0 F. for the earlier 
brood probably explains this difference. The maximum and minimum 
incubation periods were 17 and 12 days, respectively. 
Nymphal period of second brood. —The developmental period of 
the second brood varied from 20 to 24 days, averaging 21.8 days, with 
an average mean daily temperature of 72.4° F. The nymphal instars 
follow: First, 3.4; second, 3.0; third, 3.8; fourth, 4.6; fifth, 6.9 days. 
Nymphs were present in vineyards until the second week in October, 
although in relatively small numbers after the third week in September. 
Leaf surface destroyed during nymphal period. —In common 
with other leafhoppers, feeding injury is indicated upon the leaves by well- 
defined whitened areas. In order to ascertain the leaf surface destroyed 
during the nymphal period, five grape leaves upon each of which a single 
hopper had undergone its entire nymphal development were measured. 
The feeding marks were first drawn by camera lucida or by Bausch and 
Lomb microprojector at an enlargement of 15 to 24 diameters. The 
area as drawn was then measured by a planimeter and reduced 
to square centimeters. There are a number of sources of error in 
these preliminary measurements, the chief being in the use of dried leaves. 
This introduces the element of leaf shrinkage, which on comparing the 
one fresh and four dried leaves measured was found to exceed 16 per cent. 
Four dried leaves averaged 0.854 square centimeters of leaf surface de¬ 
stroyed by a single leafhopper in reaching maturity. 
Character of injury. —The character of injury caused by the three- 
banded leafhopper does not differ from that found by previous workers on 
Erythroneura comes. Reduction of functional leaf-surface from removal of 
cell sap by adult or nymph and probably from attendant injury to sur- 
