82 
BULLETIN 1176, U. S. DEPARTMENT OF AGRICULTURE 
SEASONAL OCCURRENCE 
A knowledge of the date of appearance, the maximum occurrence, 
and last records of the different stages of any insect is indispensable 
and often of great practical importance in the application of con- 
trol practices as well as in the selection of proper quarantine dates. 
EASTERN NEW ENGLAND AREA 
In order to present a general idea of the seasonal occurrence of 
Pyrausta nub Hal is in Xew England, a graph has been constructed 
(tig. 41 ) based upon the average obtained from actual observations 
APRIL MAY 
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JUNE 
18 10 
JULY AUGUST SEPTEMBEROCTOBER 
cO 31 10 20 31 10 a 
i 
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OCCURPE\CE N THE 
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; AVERAGE 
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EGGS I* GENQRATIION 
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Fig. 41.— Seasonal occurrence of the European corn borer in New England. 
Averaged from data obtained during the period 1*J1S to 19122, inclusive 
in the field and from insectarv rearings during the five-year period 
from 1918 to 1922, inclusive. 
Prior to 1922 no systematic field examinations were made with 
this particular object in view, consequently it was necessary in the 
instance of some of the stages, notably the first occurrence of eggs 
and larvae in certain years of the five-year period, to depend upon 
insectarv records, or to compute the first occurrence from the known 
presence and duration of the preceding stage in the field. This 
procedure undoubtedly affected to a slight extent the computation 
of the five-year average shown in Figure 41, consequently the average 
date of the actual presence of eggs and larvae in the field during this 
