THE ALFALFA CATERPILLAR. 5 
cage which covered an alfalfa plant. These immediately deposited 
eggs. It can be said, therefore, that the hibernating forms issue 
between March 1 and March 20. The season of 1909-10 was ex- 
ceedingly cold in the valley, while that of 1910-11 was, up to the 
middle of February, precisely ,the reverse, and up to the 8th of this 
month larve had been found present in limited numbers in the 
fields. It seems, therefore, probable that during some winters the 
species may breed throughout the entire season, as sometimes there 
is hardly a frost. Either the larval or pupal stage, or both stages, 
would during such winters be merely lengthened, for that is really 
what happens in the spring or fall of the year, and thus the insect 
could hardly be said to hibernate. However, eggs were being laid 
on March 15, and possibly a few days earlier, and these gave rise 
to the first or spring generation. This generation was very slow in 
developing, requiring about 44 days, the egg stage being 6 days, the 
larval stage 30 days, and the pupal stage 8 days. As the weather 
became warmer each of these periods gradually lessened until in the 
third generation only 22 days were required for complete develop- 
ment, the egg stage in this case being 4 days, the larval stage 12 days, 
and the pupal stage 5 days. These were the periods of development 
for individuals confined in cages; in the field a few days longer, 
often as many as four or five, seemed to be required for development 
from egg to adult. 
The first generation covered the period from March 15 to April 
30; the second generation from May 1 to May 28; the third genera- 
tion from May 28 to June 20; and the fourth generation from June 
20 to July 15. There were thus four distinct generations, the last 
being less distinct than the others. Later in the year the generations 
became so largely confused that it was impossible to separate them. 
Just as the fourth generation was beginning to pupate, the supposedly 
contagious disease before mentioned killed a large majority of the 
larve present at the time, and thus observations along life-history 
lines were checked. From this time on, scattering individuals pro- 
duced eggs and gradually increased in numbers up to October, after 
which time quite a few worms were present in some fields, and often 
considerable damage was noted. In fields that had been green dur- 
ing August, when the water supply was short in the valley, there 
were always more of these caterpillars noticed than there were in 
fields that had not been green during the month stated. This was 
due to the fact that the worms were able to feed in these green fields, 
and therefore in the fall there remained quite a number of adults. 
By the middle of October, as the nights became cool, the larve and 
pupe did not develop as rapidly as during the summer months, and 
the species just held its own in numbers up to December 28, 1910, 
when all were in the hibernating stage. 
[Cir. 133] 
