a} THE ALFALFA CATERPILLAR. 
alfalfa should be cut just when it is beginning to bloom. Other 
noticeable factors which tended to hamper control measures were that 
at haying time the crop was cut high, the turning corners were left 
ragged, and the ditch banks and borders poorly mowed, if at all, and 
thus the caterpillars that were present and had not gone through to 
the adult stage had a large amount of material upon which to de- 
velop, and soon did so, so that the butterflies from these were ready 
for the next crop. These places would also afford bloom which would 
naturally attract the butterflies. 
For fields in which good cultural conditions were to be created and 
in which methods were to be inaugurated that would not further the 
development of the caterpillars, 10 locations were selected and used 
as a basis of work. From what was said in the previous paragraph 
it will be readily seen that the thing to be done in these fields was to 
put them under a system that would remedy all or part of the defects 
noted in other fields. 
As has been mentioned before in this paper, four generations of 
caterpillars were observed in the Imperial Valley the past year 
(1910). A large part of the damage was due to the caterpillars of 
the third and fourth generations, the first and second not being 
numerous enough to assume any serious aspect. The task, then, was 
to keep their numbers below the point at which they could do any 
considerable damage. The time to start this control work was natur- 
ally with the earlier generations. The ten fields mentioned (no two 
of which had had the same conditions of culture previous to that 
year, and which had all suffered more or less damage the year before, 
namely, in 1909) were given what might be termed clean culture, or 
careful management. Just as soon as possible after removing a crop 
of hay, using the methods to be described later, the field was irrigated 
thoroughly, thus starting the growth quickly. The field was again 
irrigated as soon as the dry condition of the crop required, and thus. 
the growth was forced and not allowed to be checked. It takes about 
28 days to produce a hay crop in the Imperial Valley, a little longer 
than this in the spring and fall, and a few days less in warmer 
weather. It also takes just as many days as has been shown under 
“seasonal history” for the butterflies to develop from egg to adult. 
Now if the crop of hay be forced by frequent watering, or because 
of good soil conditions, the worms will not have gone into the rest- 
ing stage at time of cutting, but, instead, will still be feeding on the 
green alfalfa, and when the hay is cut and removed conditions are 
rendered unfavorable for their development and their food supply 
will be correspondingly reduced. Therefore, the hay should be cut 
just as it is coming into bloom, which is a few days sooner than it 
is generally thought advisable to cut it, as a generation of worms 
will take a whole field in a short time. Thus not only will the hay 
[Cir. 133] 
