THE CLOVER ROOT BORER 99 
20 days old. It is possible that oviposition in this case may have 
been done by a precocious individual of the new generation, but no 
evidence appears to indicate that such early sexual development takes 
place; whereas there is evidence that an adult, the mature form of an 
overwintered larva, might lay an egg on that date. As adults produced 
at the normal time (August or September) are known to have an 
active reproductive period of at least three months, in addition to the 
active feeding period of several months in fall and early spring (mak- 
ing an adult life of about 10 months, of which perhaps 5 are active), 
adults produced in May from overwintered larve would almost 
certainly, barring accidents, be alive and reproducing about the 
beginning of September. As the period of development from new- 
laid egg to adult is about two and a half months in spring and 
summer, larve hatched from eggs laid in the late summer and fall 
are not able to complete their development before winter causes a 
cessation of activity. Some of the offspring of these belated individ- 
uals tend to be belated also. This is a plausible explanation of the 
frequent occurrence of hibernating larve, and rather conclusive 
evidence that there is but one generation a year on red clover in 
America. Evidence in support of this theory is afforded by Parker’s 
notes at Hagerstown, Md. Parker took adults from clover roots on 
August 25, 1916, and placed them on clover roots in tin boxes. These 
individuals had laid no eggs by September 29. In another case he 
confined early adults of the new generation on clover all summer, 
but obtained no eggs in the fall. 
RATE OF REPRODUCTION 
As already noted, the female beetles mature eggs slowly, and but 
few eggs are laid in the first egg galleries during a period of three to 
four weeks in May, when the soil temperatures range low. There is 
evidence that the female changes her egg gallery two or three times 
during the reproductive period, thus occasioning delay or diminution 
of ege production. 
Experiments to determine the total progeny of one pair of borers 
were conducted at Forest Grove, Oreg., using cages of three types: (1) 
Flower-pot cages containing one or two clover plants and covered with 
a lantern globe; (2) cylindrical wire-mesh cages buried in the ground, 
planted with one, two, or three clover plants, and covered with a lan- 
tern globe; and (3) wire-screen cages 3 by 3 by 3 feet in size, lined with 
cheesecloth and placed directly over five young transplanted clover 
plants growing in the soil. Clover plants were collected from fields 
sown the previous spring, gathered before March 15, and apparently 
free from infestation. Cages were started before the first flight of 
borers, except in 1920, when the experiments began coincident with 
the first flight. Each cage contained a single pair of borers. 
The flower-pot cages dried out very rapidly in midsummer, un- 
doubtedly thereby shortening the life of the adults. The borers were 
also too closely restricted, a pair having but one or two roots to work 
on. The total progeny of one pair recovered from each of six cages 
of this type in one season was 6, 6, 3, 8, 8, and 26, respectively. 
The wire-mesh cages sunk in the ground more nearly approached 
natural conditions, but the borers were again in some cases restricted 
