18 DEPARTMENT BULLETIN 179. 
fields of small grain have been observed in which the adults and 
nymphs averaged 4 or 5 to each head of grain. On several occasions 
a quart of the insects was swept within a space of five minutes. 
After the middle of July the numbers of each succeeding generation 
are greatly reduced by the activities of parasites and predacious 
enemies until at the end of the season it is sometimes very difficult 
to find specimens.of the insects, or their eggs, in fields where they 
were formerly abundant. 
HABITS OF NYMPHS. 
GREGARIOUSNESS AND POWERS OF LOCOMOTION. 
During the first instar the young nymphs are gregarious in habit 
and seldom leave the proximity of their parent egg cluster. Soon 
after the second instar is reached they may wander away singly in 
search of food, but usually are found feeding very close together. 
During the third and succeeding instars the nymphs become more 
solitary in habit, but if the food supply is abundant the entire 
progeny of one egg cluster may reach maturity within a few feet 
from the place of their incubation, and under exceptional circum- 
stances they sometimes complete their development on the same 
plant. The nymphs are rather slow of movement and they lack the 
power of flight, but in cases of necessity the larger nymphs may 
crawl several hundred feet in search of food. 
FEEDING. 
The nymphs when feeding assume a position with the legs strongly 
braced against the plant, the head upward or downward. The setz of 
the mouth parts are inserted at right angles to the body and the liquid 
contents of the host are removed by suction. In the case of small 
grains the nymphs remove the entire contents of each kernel through 
a single puncture, but when feeding on tender stems several punctures 
are made within short distances of each other. Apparently the 
nymphs can not pierce any plant tissue after its epidermis has become 
hardened. 
In the early spring the nymphs of all stages feed upon Russian 
thistle but later in the season a large percentage of the fourth and 
fifth instar nymphs feed, with the adults, on the tender stems and 
developing heads of grain. The larger nymphs have also been ob- 
served feeding on the tender stems and newly formed seeds of 
alfalfa, but experiments demonstrated that the species could not be 
reared from egg to adult on this plant. Throughout the season the 
young nymphs of the first three instars appear to confine their atten- 
tion almost exclusively to Russian thistle, and when other food 
plants are lacking the nymphs of the last two instars feed upon this 
plant. 
he 
