PKOGKESS KEGARDING SUGAE-BEET WEBWOEM. 59 
LIFE HISTORY AND HABITS. 
In rearing experiments conducted at Rocky Ford, Colo., the average 
time required from the deposition of the eggs until the moths issued 
was a little more than a month. The egg stage was observed to vary 
from 3 to 5 days, the larva stage from 17 to 20 days, and the pupa 
stage was usually 11 clays. These variations were from records of 
successive generations. 
So far as the writer has been able to determine, there are three 
generations or " crops " of webworms in the Arkansas Valley each 
year. There may be a fourth generation, but if so it is not clearly 
marked and possibly occurs early in the season on weeds such as 
Russian thistle (Salsola tragus) and lamb's- quarters (Chenopodium 
album). For the sake of convenience we may assume that only three 
generations occur yearly. The periods during which the writer ob- 
served the webworms of these successive generations in evidence on 
sugar beets in the Arkansas Valley ranged from about the middle 
of June until early July for the first generation and from about the 
middle of July until well into August for the second generation, 
while the third brood occurred in September. 
In reality the generations are not sharply marked and considerable 
overlapping may occur. In general the danger period extends from 
shortly before the middle of June until well into September. The 
first generation of webworms may be expected at its height of destruc- 
tiveness during the latter half of June, at a time when the beets are 
comparatively small and least able to resist the attack. (See fig. 
14.) At this season the infested beets may actually be killed by this 
webworm, which, after eating all the leaves, may destroy the crown 
of the plant. Whenever the crown is destroyed the beet dies. So 
far as the writer has observed, the acreage destroyed in this way is 
very small and ordinarily occurs only when the infested beets are 
young and the available leaf surface limited. By the time the 
" worms " of the later generation are present the beets have become 
of good size and, although they may be completely stripped of all 
but the youngest leaves, it is rarely that any are killed. (See figs. 
11, 12.) ' 
The larva? of the first generation, after maturing and burrowing 
into the ground, pupate promptly and th'e moths issue within a few 
days and deposit eggs for the second generation. The " worms " of 
this next generation, on reaching maturity, likewise burrow into the 
ground and spin their tubelike cases. However, only about half of 
them pupate promptly, the others remaining unchanged in the tubes 
until the spring of the following year. From the pupae which develop 
in August, moths issue which deposit eggs for the third or September 
generation, and these "worms" remain unchanged throughout the 
