110 
BULLETIN 1476, U. S. DEPARTMENT OF AGRICULTURE 
Table 38. — Daily rate of ovisposition of P. nubilalis females, New Englatu 
1918 to 1921 
Generation 
Number 
of 
females 
under 
observa- 
tion 
Average 
oviposi- 
tion 
period 
in days 
Average number 
of days during 
oviposition on 
which no eggs 
were deposited 
Average 
number 
of eggs 
per day 
during 
oviposi- 
tion 
period 
Maximum eggs 
deposited on any 
one day (average) 
Second generation, 1917-18 
First generation, 1918 
Second generation, 1918-19 
First generation, 1919 
Second generation, 1919-20 
First generation, 1920 
Second generation, 1920-21 
11 
17 
68 
109 
121 
92 
17 
42 
12.1 
13.4 
12.7 
11.8 
14.1 
9.5 
10.6 
13.0 
Number 
3.8 
4.5 
4.8 
4.0 
4.6 
1.6 
4.6 
3.4 
Per cent 
31.4 
33.6 
37.8 
33.9 
32.7 
16.8 
• 43.4 
26.1 
28.4 
32.7 
26.4 
31.6 
25.4 
51.3 
27.4 
52.3 
Number 
87.0 
119.9 
96.0 
123.0 
80.8 
153.3 
68.2 
142. 4 
Per cent 
25.3 
27.3 
28.6 
32.5 
22.6 
31.5 
23.5 
20.9 
Total 
477 
12.2 
3.7 
30.3 
34.7 
113.1 
26.3 
The data given in this table show that for approximately one- 
third of the days of the oviposition period the moths under ob- 
servation did not deposit any eggs and that an average of from 
22.6 to 32.5 per cent of the eggs were deposited in one day by 
moths of the different generations. 
Approximately 23.7 per cent of the moths of the second genera- 
tion 1919-20 series, shown in the table, deposited the greatest num- 
ber of eggs per day during the first day of their oviposition period, 
whereas 55.1 per cent of such moths deposited the greatest number 
of eggs per day during the first five days of their oviposition 
period. One individual of this series deposited 330 of her total 
complement of 517 eggs on the first day of her oviposition period, 
and the remaining eggs were deposited throughout a period of 
14 days. The average duration of the oviposition period of this 
series of moths was 14.1 days. In the 1920 series of first-generation 
moths 42.4 per cent deposited the greatest number of eggs per day 
during the first day of their oviposition period, whereas 81.5 per 
cent of these deposited the greatest number of eggs per day dur- 
ing the first five days of their oviposition period. The average 
oviposition period of this series of moths was 9.5 days. 
The long period of fertility of the moth is important because 
it results in larvae of several instars being present in the same 
field, and often on the same plant simultaneously, thus causing a 
difficulty in evolving control measures having for their objective 
the destruction of the young larvae before they enter the plant. 
This fact also increases the opportunity of dispersion by flight 
or carriage of the gravid females. 
FLIGHT 
The moths are essentially nocturnal in habit, although individuals 
have been observed taking short flights during daylight. Normally, 
however, they seek shelter during the day underneath the leaves of 
weeds, grasses, and cultivated crops. They are often found lurk- 
ing in the grass headlands adjacent to fields, of corn and other 
crops. When disturbed during the day, they make short flights, 
close to the ground, for distances of from 10 to 20 feet, and eventually 
seek cover a^ain. 
