THE CLOVER ROOT BORER 25 
LARVAL PERIOD 
~ . The larval period varies with the conditions under which the larvee 
-develop, both temperature and the condition of the host root being 
“factors of importance. The shortest larval period, passed in a bare 
piece of clover root, contained in a tin salve box on an insectary 
-- bench, was estimated at 32 days, that is, 42 days hatching to callow 
~ adult, less 10 days pupal period, June 13 to July 25,1917. Other 
‘individuals under similar conditions had larval periods of 39 to 65 days. 
When the newly hatched larvee were placed in artificial pockets formed 
with a needle in young living clover roots, the openings plugged, and 
the plants grown in the insectary, the following larval periods were 
recorded in June, July, and August, 1919: 55 days minus (fresh 
pupa), 52 days plus (prepupal larva), 46 days plus (well-grown larva), 
62 days minus (fresh pupa). These results indicate a larval period 
of at least 50 days under nearly natural conditions for development. 
Seasonal field records indicate a minimum larval period of about this 
length, or nearer 60 days for the Willamette Valley, more than 40 
days jor Hagerstown Md., in 1916, according to notes made by 
H. L. Parker and W. E. Pennington, and about 40 days for Wooster, 
Ohio, in 1898, according to notes made by Webster and C. W. Mally. 
Later in the season, when temperatures are lower, in cold or shaded 
soil, on large, healthy roots little affected by borer attack, field records 
show that the larval period is prolonged. Such records indicate that 
borers develop more rapidly on dying roots than on healthy roots. 
Observations in a field containing many dying and dead plants indi- 
cated that most of the root borers attained the adult stage by the 
middle of September, at the same time that roots in neighboring 
fields where most of the plants were still living contained many larve 
and pupe. 
PUPAL PERIOD 
The pupal period was determined by placing naked pups, whose 
date of entering pupation was known, on a piece of moist blotter or 
moistened plaster of Paris in a tin salve box kept on a bench in a 
screened insectary. The pupal period was determined as 10 days, 
from August 17 to August 27, 1917. In September and early Octo- 
ber the pupal period was often 12 to 13 days. Webster and Mally 
recorded a pupal period of 7 to 11 days on moist sand at Wooster, 
July 6 to July 13, 15, and 17, 1896, observing pupz of unknown date 
taken from roots. H. L. Parker noted a pupal period of 7 or 8 days 
in the early part of August, 1916, at Hagerstown, Md. 
Adults fresh from the pupal stage are of a pale creamy white color, 
and several days elapse before they become sufficiently chitinized to 
feed on the clover roots. 
By reviewing the life history of this species, it may be observed 
_ that its development is a very extended process. Field and labora- 
_ tory records indicate a total period from fresh-laid egg to adult of 
60 or more days at Hagerstown, Md., and Wooster, Ohio, and at 
least 70 days, or even as much as 90 days or more, in the Willamette 
Valley in Oregon. The life history and seasonal occurrence of the 
clover root borer are illustrated graphically in Figure 11. 
