JOURNAL OF ECONOMIC ENTOMOLOGY 
140 
[Vol. 17 
from the material below ground by early June irrespective of the time 
or season of ploughing. 
Of the larvae which come to the surface of the ground a small propor¬ 
tion enter the crop refuse still on the surface, an undiscoverable few 
probably migrate from the field, but what actually becomes of the great 
proportion of them is in large measure unknown. Studies at the end 
of the spring season in 1923 when the material below ground was 
examined show that larvae are not present in any numbers in the deeper 
levels of the soil, and a sifting of 900 square feet of the surface soil in 
representative situations to a depth of 2 inches recovered but two larvae. 
Examination of the grass in the headlands yielded no larvae, and cages 
set to recover emerging adults on the soil itself, on the headlands, and 
in the standing oat crop on that part of the field not used in the experi¬ 
ments failed to yield a single adult. Hence it is assumed that in some 
way as yet practically unknown, the larval population on the surface 
of a field is virtually wiped out. 
Experiments designed to determine the possibility of moths emerging 
from the material below ground were carried on. In these it was noted 
that unless the larvae were about to pupate when buried they came to 
the surface with great promptitude from depths up to 12 inches. Where 
the larvae were in the pre-pupal stage many of them pupated and produc¬ 
ed moths as did buried pupae. In one experiment three of these adults 
did make their way to the surface from burials of pupae at depths of 1 
and 2 inches in a study involving 110 pupae in their natural tunnels in 
pieces of stalk at depths of from 1-12 inches. As a rule, however, the 
moths could but rarely escape from the stalks into the soil and died in 
the tunnels into which they had emerged. In some cases they did man¬ 
age to get out short distances into the soil but died just outside the stalks. 
From work carried on in 1923 by Mr. G. J Spencer and Mr. G. Wishart 
of the Ontario Department of Agriculture it was determined that by 
suitable caging it was possible for larvae where deprived of more suitable 
shelter, to pupate and produce moths in bare sandy soil if placed under 
these conditions just previous to pupation. These studies also showed 
that a few moths were liable to mature from high concentration of 
larvae coming from material below ground. In this experiment a 
burial of 2,000 larvae per 100 sq. feet was made in the early spring and 
clumps of spring grains and piles of stones were arranged upon and about 
the burial and later caged. Fifteen adults in all were secured in 20 
cages, 10 of these moths were from a two foot square plot of oats 
planted on top of the burial itself. Thus there is always the danger of 
