972 
Journal of Agricultural Research 
Vol. V, No. 21 
Abdomen with five distinct tubercles on each side, the one pair caudad of the cornicles 
and the most cephalic pair about equal in size and larger than the three median 
pairs. Cornicles (PI. LXXIV, fig. 12) subcylindric, largest at the base, tapering 
slightly distad, slightly flanged at the tip and strongly imbricated, 0.398 mm. in 
length. Anal plate rounded, setose, and armed with about a dozen long curved hairs. 
Cauda (PL LXXIV, fig. 19) elongate, rounded distad, sometimes slightly constricted 
in the middle, setose, and armed on each side with about five long, curved hairs; 
length, about 0.176 mm. Legs slender, hairy, particularly the tibiae; length of hind 
tibiae, 0.837 mm.; hind tarsi, 0.112 mm.; length of insect from vertex to tip of cauda, 
2.56 mm. 
Color characters: General color very variable, from a light green to a very dark 
green. Head orange-yellow, sometimes with a purplish cast. This orange-yellow 
head is in many specimens much more pronounced than in others. Thorax similar 
to the head in color, shading off into yellowish green at the abdomen. Both head 
and thorax covered with a slight bloom. Abdomen light green. Antennae yellowish, 
dark toward the tip; tarsi, cornicles, cauda, anal plate, distal extremities of femora, 
and proximal and distal extremities of the tibiae black. Labium tipped with black. 
In specimens which have not been well supplied with food and which consequently 
are much stunted in growth, the colors are much deeper, the green being very dark 
over the entire bbdy, whereas in well-fed, large specimens the color is light green. 
Late fall specimens which are exposed to low temperatures have a brownish cast. 
OCCURRENCE 
As stated previously, this was by far the most common form occurring 
during the summer. Moreover, in so far as the actual propagation of 
the species is concerned, it is the only summer form necessary, since we 
were able, without difficulty, to carry insects from the stem mother to 
the sexes without the intervention of a single winged individual. For 
the spread and consequently the greatest development of the species, 
winged summer forms seem necessary, since at the present time it has 
no other natural mode of becoming wholly disseminated. In nurseries 
the wingless insects may travel from tree to tree in the rows, and trees 
bearing eggs may be shipped to different parts of the world. Such dis¬ 
semination, however, would be of little avail to a purely wingless species, 
as compared to one containing winged forms, since its attack thereafter 
would be confined to trees on which it was shipped, or at most to a few 
surrounding trees. 
LENGTH OF NYMPHAL LIFE 
The average duration of the nymphal period in this form was 7 to 8 
days, the time being equally divided between the four stages. During 
the hot weather occurring in the last of June and first of July this period 
was shortened to 6 days, and in one instance an insect commenced repro¬ 
duction when only 5 days old. On the other hand, with the beginning of 
cooler weather in the late summer the period exceeded this average. 
About September 1 the time occupied by the nymphal stages was from 
8 to 9 days. This period gradually increased in length till the last of 
September, at which time it covered n days. During the month of 
