- 10 
Where Eggs Are Laid 
Egg laying in alfalfa fields was confined almost entirely to dead, 
dry alfalfa stems composing the surface litter. Only a few clusters of eggs 
were encountered in living alfalfa stems or in living or dead grass stems. 
About 95 percent were deposited in small, dry, easily punctured stems 1.5 mm. 
and less in diameter. Eggs were deposited in clusters ranging in size from 
1 to 46 but comparatively few contained more than 25. The average cluster 
in dry stems of alfalfa fields contained 14.3 eggs. 
Early egg laying in sourclover was also confined mostly to dead stems, 
but by early March the majority were contained in the growing stems, indi- 
cating a marked difference in adult reaction to the two hosts. The fact that 
virtually no eggs were found in stems of growing alfalfa suggests the possi- 
bility that this plant is an unsuitable host in this respect. This ap- 
parent reaction of the ovipositing adults to sourclover is closely analogous 
to the oviposition habits of Hy pera postica on alfalfa in Utah and other 
States. 
Incubation Period 
The incubation period was determined under insectary conditions 
where temperatures closely approximated those in the field. Eggs were ob- 
tained from oviposition cages and incubated in salve jars on moist blotting 
paper. Moisture was added in small amounts as needed until hatching ceased. 
Except in a few instances, eggs for this study were obtained only from 
adults caged on alfalfa. 
During most of January, when the prevailing mean outdoor temperatures 
were about 54° F., incubation required 20 to 22 days, but slightly warmer 
weather late in the month and early in February shortened the time to 16 to 
19 days. By early March the incubation period had shortened to about 10 days 
and by early April, with outdoor mean temperatures of about 75° F., it was 
only about 6 days. Incubation of several series of eggs late in the season 
from alfalfa, sourclover, and hubam indicated that the host plant of the 
parent adult had no significant bearing upon either the incubation period 
or the viability of eggs. Data on the incubation period are presented in 
table 2. 
THE LARVAL STAGE 
Information concerning the larval stage (fig. 1, D) was obtained 
through measurements of larval head sizes, laboratory rearings, and periodic 
ecological samplings of alfalfa fields and sourclover patches, supplemented 
by general field observations. 
Description of the Larva 
Measurements of head sizes definitely showed that Hypera b runne ipen nis 
has four larval instars. Small numbers of measurements at intervals through- 
out the season showed no variation either in the number or the head size of 
