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Studies in 193^ 
Beetles emerging in 193& in southern Wisconsin belonged to "brood 
B«. Ordinarily this is the smallest of the three broods, but in certain 
years,, such as 1936, the emergence of Phvllophaga tristis, which has a 
2-year cvcle, has increased the magnitude of the flight of "brood B» con- 
siderably. The methods of study were essentially the same as those used 
in 1935 and insofar as possible beetles were collected from the sane groves. 
Species of beetles other than P. tristis were scarce in 1936. and it was 
necessary to examine a great many plants in each locality in order to obtain 
them in any quantity. All plants in each grove were examined carefully and 
it is believed that a lorge proportion of the beetles present were actually 
collected. The scarcity of beetles did not nullify the value of these 
collections but in some respects was advantageous, especially in the deter- 
mination of host preferences, since it was not necessary to omit from our 
calculations the large numbers of beetles which, in seasons of abundance, 
cannot be collected or counted. 
|light.— The collection of beetles and the study of flight were 
hindered by the occurrence of many cool nights, which prevented or retarded 
the emergence of the beetles. Considering the season as a whole, however, 
the flight of Phyllophaga tristis was very large. Beetles of this species 
were found in great numbers in various parts of Dane and Lafayette Counties, 
and many oaks, stripped or partially stripped by then, were observed in 
these localities. Damage to oaks was reported from Jefferson and Waushara 
Counties, and specimens were sent in by county agents and other persons from 
Pepin, Trempealeau, Vernon, Sank, and Eau Claire Counties. 
The first flight of June beetles was observed on May 6 at Gays Mills, 
but some beetles were taken from beneath leaves early in April. 
It was estimated that over 95 percent of the beetles flying bclongod 
to the species Phyllophaga tristis and that over 95 percent of the beetles of 
this species fed on oak. The flight of P. tristis continued until the end of 
June but flight of the other species was practically over by June 10. 
Phyllophaga tristis flew freely and mated earlier in the season and 
at lower temperatures than did the other species. Mating was observed at 
temperatures as low as 52° F. early in the season, but later this temperature 
was too low for even a small flight. P. tristis usually began issuing from 
the soil from 10 to 20 minutes earlier in the evening than did the other 
species. Early in the season emergence began at about 7:30 p.m., but as the 
length of the days increased emergence began later. With the exception of 
that by P. tristis very little mating was observed and that observed occurred 
late in the season. 
