1924] Winter Mortality of European Corn Borer 281 
In the following account of winter mortality of the European 
corn borer, information has been obtained in two ways. Field 
counts of larvse in the spring have usually been made in localities 
where the insect occurs abundantly and in host plants that have 
remained undisturbed. Over much of the area now infested 
in New England, however, the insect occurs in insufficient num- 
bers to permit such counts in numbers large enough for accuracy. 
In this case experiments were placed in the field in representative 
localities in the fall after activity of the insect had ceased and 
collected in the spring before activity was resumed. In the 
studies of the results obtained in this work, the conditions found 
to exist in the spring of 1922, 1923 and 1924 may be considered 
separately. 
Observations in the spring of 1922. 
During the spring of 1922 observations of winter mortality 
were confined to host plants that had passed the winter undis- 
TAELE No. 1. 
Winter Mortality Found in the Spring of 1922 in Several Host 
Plants that had Passed the Winter Undisturbed. 
Host Plant 
No.oi 
localities 
Total 
No. 
larvae 
examin- 
ed 
No. 
larvae 
dead 
Aver. % 
winter 
mor- 
tality 
Greatest 
% winter 
mor- 
tality 
for any 
locality 
Least 
% winter 
mor- 
tality 
for any 
locality 
Sweet Corn 
Cocklebur 
9 
901 
100 
11.1% 
16% 
6.2% 
(Xanthium sp.). . . . 
Barnyard Grass 
(Echinochloa crus- 
5 
644 
m 
5.1% 
7% 
2% 
galli (L). Beauv). 
Smartweed 
4 
273 
30 
10.9% 
13% 
10% 
(Polygonum sp.).. . 
Beggar-ticks 
2 
150 
4 
2.7% 
4% 
0% 
(Bidens sp.) 
Pigweed (Amaran- 
thus retroflexus 
2 
210 
16 
7.6% 
8% 
0% 
L.) 
Lamb’s quarters 
{Chenopodium al- 
2 
200 
42 
21% 
27% 
15% 
bum L.) 
1 
100 
8 
8% 
