PROGRESS REPORT OX THE EUROPEAN CORN BORER 149 
500 per cent for the area, when compared with conditions existing in 
1925 (based upon larval population). Should the rate of annual 
increase which prevailed during the years 1923 to 1926 be continued, 
it appears reasonable to expect that losses will become general 
throughout this area in the near future, unless recommended control 
practices are strictly and generally followed. 
An analysis of the data from 46 townships in New England showed 
a decrease of 38 per cent in intensity of infestation for 1926 as 
compared with 1925 (based upon larval population). Great decreases 
were especially apparent in commercial sweet corn plantings where 
an average of 20 per cent ear infestation existing in 1922 had been 
reduced to approximately 5 per cent in 1925 and to slightly less 
than 5 per cent in 1926. Similar reductions of infestation and 
damage were observed in susceptible vegetables and flowers, par- 
ticularly in beets, beans, celery, rhubarb, potatoes, gladioli, dahlias, 
asters, and greenhouse chrysanthemums. 
Detailed studies pertaining to the effect of borer injury to the 
cornstalks on the number, weight, and quality of ears, and on the 
grain produced, have demonstrated that this indirect injury usually 
is far more important than the direct injury to the ears caused by 
the larvae feeding thereon. 
A remarkable decrease has been observed in the larval populations 
in areas of weeds and large-stemmed grasses formerly existing in 
the New England area. This former source of infestation, from 
which large numbers of moths issued to deposit their eggs upon 
cultivated crops, has been removed as a result of the enforcement 
of the Massachusetts law requiring clean-up action, plus the ex- 
perience of local vegetable growers who have learned the necessity 
of clean culture. 
SEASONAL HISTORY 
Only one generation annually of the corn borer lias developed 
in New York (not including the New York Bay area), Pennsyl- 
vania, Ohio, Michigan, and Indiana, although occasional instances 
of summer pupation, denoting a two-generation tendency, have been 
observed each year. 
Two generations have developed both in New England and in the 
scattered infestations in the New York Bay area each year, although 
the percentage of individuals developing a second generation has 
varied from 40 to 100 per cent in different years. No indication 
of a third generation was observed in 1925 or 1926. 
An analysis of meteorological data for New England with refer- 
ence to the generation cycle has shown that a preponderance of pre- 
cipitation, coupled with normal temperatures in March, April, and 
May, and followed by a dry June, induced an early start of the corn 
borer in New England. Under these conditions a complete second 
generation has developed. On the other hand, a deficiency in precipi- 
tation during March, April, and May, followed by a rainy June, was 
unfavorable to the insect. Under such conditions there" has been a 
diminution in the number of individuals developing a second genera- 
tion, with a consequent reduction of injury caused by the insect. 
Single-generation material transferred to a two-generation area in 
1920 and reared continuously there in large field cages retained its 
