88 BULLETIN 1476, U. S. DEPARTMENT OF AGRICULTURE 
tions, although six and seven molts before pupation were recorded 
by a few individuals of the first generation, and a few of the reared 
larvae of the second generation recorded five and six molts before 
reaching full growth preceding the period of winter inactivity. The 
average duration of the pupal period each year varied from 9.86 
to 11.04 days for the females, and from 9.24 to 12.61 days for the 
males of the first generation, and averaged from 18.12 to 19.14 days 
for the females, and from 19.04 to 20. 71 days for the males of the 
second generation. The average duration of the preoviposition 
period each year varied from 2.6 to 4.3 days for the first genera- 
tion, and from 4.1 to 5.1 days for the second generation. The average 
total life cycle of the first generation, from the egg to the termina- 
tion of the preoviposition period of the female, varied each year 
from 49.56 to 57.6 days for the majority of the individuals under 
observation. The duration of the total life cycle of the second 
generation includes the winter period of inactivity and can not, 
therefore, be accurately expressed. 
The duration of the egg stage was obtained by isolating individual 
egg clusters in small salve-box and plaster-of-Paris cages as soon 
as deposited by females in confinement. 
The duration of the larval instars was determined by isolating 
newly hatched larvae in cages containing stems and leaves of corn and 
other favored food plants (Rumex and Amaranthus). After the 
larvae entered these plant portions it became necessary to make daily 
dissections in order to determine molts. This procedure resulted 
in a heavy mortality of the larvae under observation, and undoubted- 
ly prolonged the duration of the instars of the surviving larvae. 
No satisfactory rearing cage or rearing method has yet been devised 
which will permit frequent examinations of P. nubilalis larvae for 
molts without disturbing the feeding larvae to such an extent as to 
affect their normal development. Therefore, for this reason alone, 
the average for the total period of larval development in each 
generation shown in Table 24 probably varies to a considerable 
extent from the actual duration of the larval period in the field, 
in the case of individuals exposed to comparable conditions of tem- 
perature, humidity, etc. 
The duration of the pupal period was obtained by isolating full- 
grown larvae in individual glass-tube cases and noting the pupal 
formation and adult emergence. 
The duration of the adult stages was determined by confining pairs 
of newly emerged adults in individual lantern-globe cages placed 
over flowerpots filled with soil and containing a branch of Rumex 
or Amaranthus inserted in a tube of water buried in the soil. In 
this type of cage the females deposited eggs freely upon the leaves 
of the plant, and in many instances upon the sides of the lantern 
globe, as well as upon the cheesecloth with which the top of the cage 
was covered. The soil in the flowerpots was kept moist, and small 
wads of cotton soaked with water were also placed in the cage, thus 
providing necessary moisture for the confined adults. 
NEW YORK 
Table 25 gives a rather incomplete record of the average duration 
of P. nubilalis stages at Silver Creek, N. Y., as obtained from in- 
sectary rearings during the period from 1922 to 1924, inclusive. 
