106 BULLETIN 1476, U. S. DEPARTMENT OF AGRICULTURE 
MATINGS NECESSARY TO FERTILIZE TOTAL COMPLEMENT OF EGGS 
A single mating was found to be sufficient to insure the normal 
percentage of fertility of the total complement of eggs deposited by 
each female in a series of experiments wherein single pairs of newly 
emerged moths were confined in separate lantern-globe oviposit ion 
cages. Each of these cages contained a virgin female, which had 
emerged from an individual glass vial cage, and a male which had 
emerged from similar cage. These cages were kept under observation 
and as soon as copulation occurred the male was removed. It is 
not known whether more than one mating normally occurs in the 
field, but in confinement several matings have been observed in 
instances where pairs of moths were retained in cages throughout 
their period of life. The fact that a single mating appears to be 
sufficient to insure the fertility of the eggs apparently would enable 
gravid and fertilized females to perpetuate the species if dispersed 
for a long distance by flight or by carriage. 
NUMBER OF FEMALES FERTILIZED BY EACH MALE 
In order to determine the number of females fertilized by each 
male, a vigorous newly emerged male was placed in an oviposition 
cage with a newly emerged female. As soon as copulation occurred, 
the male was transferred to a similar cage also containing a virgin 
female. This process w T as repeated until the death of the male 19 
days from the start of the experiment. During this period the male 
had mated with nine different females. The total complement of 
eggs deposited by the second, third, fourth, and sixth females used 
were fertile, whereas the eggs deposited by the first, fifth, seventh, 
and ninth females used were infertile. The eighth female died with- 
out depositing eggs. The other females in this series deposited a 
normal number of eggs. It w T ill be noted, therefore, that the Pyrausta 
nubilalis male used in this experiment fertilized a total of four 
females. Even allowing for cage conditions, it seems probable that 
under natural conditions each male would fertilize several females. 
OVIPOSITION 
The average preoviposition period of P. nubilalis females in 
confinement varied from 2.6 to 5.1 days in Massachusetts, as shown 
in Table 24. Among the females under observation in confinement 
and in the field, oviposition was greatest during the period between 
dusk and midnight, and rarely occurred during the daylight hours. 
The eggs usually are deposited upon the undersides of the leaves 
of the host plant, although they have been found infrequently on 
the upper sides of the leaves and upon the stems of plants such as 
corn, rhubarb, and cocklebur, as well as upon the husks of ears of 
corn. 
During the act of oviposition the female extrudes the ovipositor 
until its tip comes in contact with the leaf blade at the spot selected 
for egg deposition. She then stands still and vibrates the abdomen 
until the spherical egg appears at its tip. The egg is then quickly 
pushed against the leaf and tamped into place with the ovipositor. 
This operation changes the egg from its orginial spherical shape into 
a more flattened one. The remaining eggs of the cluster are then 
