- 5 - 
A few adults fed by day, but the heaviest feeding occurred at night, 
especially during the late spring when daily maximum temperatures approached 
or exceeded 100° F. During such temperatures adults preferred to remain 
under cover on or near the ground in comparative inactivity. When the cover 
in feeding areas was inadequate, adults concentrated in nearby grassy areas or 
in soil cracks during the day and returned at night to resume feeding. 
An occasional adult aestivated in feeding areas where adequate ground 
cover existed, but virtually all left these areas to congregate in situations 
affording more suitable protection. A few individuals remained active in 
fields and could be swept from them at night until the hay harvest late in 
June. Thereafter, neither sweeping nor examination of debris from fields 
revealed adults. 
The few weevils remaining active in the field developed sexually to 
som.e extent, some of the females attaining the state of developing ova and 
even full-sized eggs. Dissection of these adults revealed apparent dis- 
integration of the sexual system, and apparently all died, since none was 
found to be intermixed with aestivating weevils. Moreover, the practice of 
abandoning alfalfa fields, with consequent absence of succulent food and 
cover during the heat of the summer and early fall months, militates against 
survival of these adults. Two seasons' study of these abnormal individuals 
shows conclusively that they are unimportant under Yuma Valley conditions. 
Abundance of Adults 
Late in April in 1939, extremely large num.bers of adults congregated 
by day in grassy borders surrounding alfalfa varietal rows on the University 
of Arizona Valley Experiment Farm at Yuma. Considerable numbers also re- 
mained hidden about the base of alfalfa crowns. At night, alfalfa plants 
nearest to grassy areas were literally covered by adults, some plants having 
an estimated 200 to 400 on them, v/hich resulted in rapid defoliation. Samples 
from a sourclover breeding area in a pecan grove on April 30 contained an 
average of 72 adults per square foot. Adults crawled promiscuously on the 
ground and even in the trees. A nearby Bermuda grass lawn, with a sparse 
mixture of sourclover, contained 13 adults per square foot. Adults were 
fairly numerous on the University of Arizona Mesa Experiment Farm and the 
Oasis Ranch near the city lim.its of Yuma, but otherwise were scarce through- 
out the infested area. In alfalfa fields adjacent to the most heavily in- 
fested areas com.paratively few adults existed. This was attributed, in part 
at least, to heavy migration following earlier harvest of the first hay crop. 
In 1940 the production of adults was greatly curtailed because 
of a high mortality of the larvae. By way of com.parison with 1939, con- 
tinuous sampling of the most heavily infested sourclover breeding area on 
the Arizona Valley Experim.ent Farm showed a peak abundance of only 4 adults 
per square foot. Samples from the most favorable cover areas therein showed 
a peak of only 7 per square foot. In alfalfa varietal plots and nearby 
alfalfa fields adults were actually difficult to collect by sweeping methods. 
