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In addition to shaking the limbs of preferred host trees and shrubs 
over canvas, from two to five collectors picked beetles by hand from all 
kinds of hosts on which they were found. Attempts were made early in June 
to devote a definite amount of time to each species of host, "but variation 
in population was found to induce either such dispersion or such concentra- 
tion of the beetles on their various hosts that the amount of time spent in 
this way gave a poor idea of host preferences or total populations. After 
July 1,' when beetles became considerably reduced in numbers, an area was 
entered, its host plants were listed, and all beetles observed within reach 
were removed from each host. Several persons often collected from different 
species of hosts simultaneously and often from the sane species of host so 
that the total number of beetles taken should average into figures upon which 
a fair estimate of the relative abundance of the species of beetles upon 
certain species- of hosts could be based. This method seems to give a definite 
indication of the relative importance of each species of host in each area as 
a source of food for the beetles, and for this reason these counts seem partic- 
ularly valuable. 
At present the authors know of no method of estimating accurately the 
population of the various species of Phyllophaga . based solely on counts of 
the feeding adults; however, larval counts and counts of adults in the soil 
made before emergence, in the same areas in which flights are observed, should 
increase the accuracy of estimates. These additional counts should also be 
valuable in improving estimates of host preferences. 
Flight . — Small flights of beetles occurred when air temperatures were 
as low as 54° P. One fair-sized flight began at this low temperature near 
Blue Mounds, Wis., on June 22, 1935* "but the soil tenperature on this occasion 
was 60.8°, Air temperatures above 60° are favorable for fairly large flights, 
and these increased at temperatures of 6 5°. .or above. Mating by species other 
than Phyllophaga t ristis was heaviest at 67 to 71°« When, later in the 
season, higher temperatures occurred, beetles were not so abundant and it 
could not be determined whether these higher temperatures were more favorable 
to flight than the lower ones. In Eay and June many nights were too cold for 
flight and there were heavy rains which in some cases depressed the tempera- 
tures and intefered with flight. Light showers interfered very little with 
flight, provided the temperatures were high enough. After the first of July 
temperatures were high enough to permit flight almost every night, but by this 
time most of the beetles had died. 
Population .— A total of 12,053 beetles were taken by hand picking and 
in a few cases by shaking of branches from determined hosts as given in table 
1, which also shows the percentage of the total represented by each species 
in the collections before July 1, after July 1, and for the entiro season. 
The most abundant -species at all tines were Phyllophaga rugosa (Molsh. ), 
P. hirticula Knoch, and P. fusca (Proel. ), in the order named. £. tristis 
was fourth in abundance before July 1 but fifth after July 1, and for the whole 
season was replaced by P. implicita (H m). These five species made up 98.13 
percent of the total number of beetles taken before July 1, 97. 90 percent of 
the total taken after July 1, and 98.09 percent of the total taken during the 
whole season. 
