PEOGEESS EEPOET ON THE EUEOPEAN COEN BOEER 
75 
eastern Massachusetts than in the western New York area of infesta- 
tion, yet in eastern Massachusetts there are normally two generations 
a year, or at least a preponderance of individuals which develop a 
second generation, whereas in western as well as in eastern New 
York but one generation occurs, judging from the observed be- 
havior of the insect. 
Table 21 gives a partial list of the localities where Pyrausta 
nuhilalis is known to occur, with the corresponding number of gen- 
erations annually. The data concerning the number of generations 
in the various localities have been taken from miscellaneous sources 
of information and, of course, represent only generalized conditions 
owing to the fact that in many of the foreign localities the field 
records of seasonal history, occurrence, and behavior are in many 
cases insufficient, and possibly inaccurate. 
Table 21. — Number of generations (annually) of Pyrausta nubilalis in various 
localities from which data are available 
Locality 
Num- 
ber of 
gener- 
ations 
. Remarks 
New England 
2 
1 
1 
1 
1 
1 
1 
2 
1 
1 
2 
1 
1 
1 
2 
1920, 1 1 complete and 70 per cent of a second generation; 1921, 2 com- 
Eastern New York 
Western New York 
Pennsylvania 
plete and a small partial third; 1922, 1 complete and 86 per cent of a 
second generation; 1923, 1 complete and 60 per cent of a second gen- 
eration; 1924, 1 complete and 78 per cent of a second generation. 
One complete and a small partial second generation in 1921. 
Do. 
Do. 
Ohio.. 
Do. 
Michigan 
Do. 
Ontario, Canada 
Southern France 
Northern France 
Southwestern Russia 
Transcaucasia. . 
Do. 
ProDably a partial second generation during favorable seasons. 
Belgium 
Netherlands 
Hungary... 
Italy 
A third generation is reported from environs of Florence. 
1 Two complete generations and a small partial third generation were reared in the insectary during 
1918, and two complete generations were reared under the same conditions in 1919, but extensive field 
studies to determine generation development were not initiated until 1920. 
SEASONAL DEVELOPMENT 
Since the corn borer appears to be more destructive and presents 
a more difficult problem in localities having two generations in this 
country than in those having one generation, obviously it is a matter 
of economic importance to ascertain, if possible, the factors that 
determine the number of generations in localities within its present 
distribution. This information is necessary in order that the prob- 
able seasonal history of the insect may be forecast for various 
sections of the United States, should the insect become widely 
distributed. The solution of this problem has been approached from 
various angles. 
The possibility that distinct biological species inhabit the New 
York and Massachusetts areas, which are one and two generation 
localities, respectively: The results have shown that individuals 
taken from both areas, as well as individuals from various foreign 
localities, crossbreed and are capable of producing fertile eggs. 
The project of rearing these hybrids is still under way. 
