JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 17 
334 
nearly uniform as it was possible to obtain, and measured; one-acre 
plots were staked out. On each plot conditions of growth were noted 
throughout the period of development of all three crops for the season, 
and during the period of growth of the first crop larval counts were made 
each alternate day after the alfalfa became tall enough to sweep with a 
net. The fact that results in former years had appeared to be good for 
a time after spraying indicated that possibly an additional spray ap¬ 
plication was needed. This possibliity was supported by the fact that 
field examinations during the two previous years had disclosed large 
number of freshly deposited eggs in the stems after the spray had been 
applied. Among other experiments it was therefore determined to try 
applications of one and two sprays and to check the results of each 
against an untreated plot. For the purpose of this discussion no 
mention will be made of plots other than numbers 1, 3, 5 and 6. 
Plat No. i was sprayed May 24th with calcium arsenate at the rate of 
two pounds per acre. A pressure of 225-250 pounds was maintained. 
On that date the alfalfa was a little less than knee high, and blossom 
buds were just plainly visible in the tips without careful inspection. 
Bud clusters were not separating and no color was showing in any of 
the buds. Larval injury was general over the entire plot, though not 
severe, and there was no noticeable checking of growth. Most of the 
larvae were large in size, some nearly full grown and rarely a cocoon 
was observed. It was a striking fact that injury that necessitated a 
spray was caused by early-hatched larvae, and that those representing 
the main part of the brood had not yet appeared, even in an early stage. 
(Fig. 9.) Observations on the check plot throughout the season 
showed that without spray little growth was made after the date men¬ 
tioned above, altho the height of larval emergence did not come until 
21 days later, so that a field that had been sprayed just preceeding this 
height would have been so severely injured as to not make recovery. 
After spraying, the alfalfa on plot No. 1 grew almost normally for a 
time, and rapidly recovered from the previous injury. On June 6th 
it was noted, however, that the green growth had been made since 
spray was applied was being attacked and a second spray application 
was made on June 7th (Fig. 10). At that time the alfalfa was a little 
more than knee high, blossom buds were broadly separated and an 
occasional one showed the color of an opening blossom. The majority 
of the larvae at that time were small, were but recently emerged and 
represented a portion of the main brood. At cutting time this plot 
was about one-half in blossom; foliage was a green, healthy color and 
