The European Corn Borer. 21 
OATS. 
Stems have occasionally been found infested when plants were 
growing as volunteers in waste places or among other crops. De- 
tailed examinations of oat straw grown experimentally within the 
infested area also revealed borers present in both baled and loose 
straw at the rate of 8 borers to 100 pounds of baled straw and 11 
borers to 100 pounds of loose straw. (Fig. 18.) 
SEASONAL HISTORY AND HABITS. 
There are usually two complete generations annually of the Euro- 
pean corn borer in the New England area of infestation, according 
to observations made since the discovery of the insect in 1917. This 
habit is subject to some variation, however, in accordance with sea- 
sonal climatic fluctuations. In 1920 only one complete generation 
and a partial second generation were produced, while in 1921 two 
complete generations and a 
partial third generation de- 
veloped. 
In the two areas of infesta- 
tion in New York, one com- 
plete generation each year was 
produced in 1919 and 1920, 
while in 1921 one complete 
generation and a limited par- 
tial second generation devel- 
oped. 
In the recently discovered 
areas infested by the European 
corn borer in Pennsylvania, 
Ohio, and Michigan there de- 
veloped during: the season of 
1921 one complete and a lim- 
ited partial second generation. 
NEW ENGLAND AREA. 
The European corn borer 
passes the winter as a full- 
grown larva or borer within 
the tunnel made in its host or 
shelter plant during the pre- 
vious summer and fall. The 
presence of such borers may 
be detected readily by small TS 1G. Chrysanthemum stem tunneled by 
nas furopean corn borer. (One-half natural 
holes on the surface of in- size.) 
Tested plants, with masses of 
the frass, or castings of the borers, extruding therefrom. This 
frass is usually white or light brown and closely resembles saw- 
dust. Upon cutting open these plants, the borers (Fig. 19) will be 
found within. 
At this time the borer is nearly an inch long and one-eighth of an 
inch thick. The head is dark brown or black. The upper surface 
