aa 
Soil populations of Japanese beetle at stations within 10 
Witte 4. rd & 
miles of orieinal center of spread 





Average population e foot 
Pericd New Jersey Pennsy lvania 
. stations stations General 
sept. 1-15 6.6 9.9 8.5 
16-30 126 10.4 9.0 
Hct. 1-15 6.9 1636 8.8 
16-31 6.8 91 8.0 
Nov. 1-15 6.9 8.6 hea 
16-30 6.4 O12 Ties 
Dec. 1-15 ae6.7 Te G75 
Jane 1-15 635 StS 7.4 
16-31 a 4.9 B07 26.8 
Mar. 16-31 De. 6.6 539 



& Records not quite complete. 
These records indicate an apparently steady decrease of ponula- 
tions during the winter. The general average number of larvae per 
square foot late in March was about 6, whereas in November it was about 
7.5, indicating an apparent winter aMuke an of approximately 20 per- 
cent. The decrease recorded for January is 9 percent, and a further 
decrease of approximately 11 percent in February and March is indicated. 
These figures are based on relatively few surveys and experience has 
Shewn that surveys made in March may not necessarily give a true indi- 
cation of the actual situation, since soil and weather conditions gen- 
erally obtaining during this month are frequently rather unfavorable 
in making accurate grub surveys. 
Records of annual fluctuations in population, which involve com- 
parisons of more than a single brood, are available only in seasonal 
surveys. A comparison of these records for March 1933 and 1934 follows: 
Soil-population frequencies of Japanese beetle in March 1933 




and 1934 54 
os average soil po,ulation per 
Stations Period squure foot 
1933 | 1934 
General March 16-31 10st 5.9 
New Jersey March 16-31 7.0 Fad. 
Pennsylvania March 16-31 13.2 6.6 

ee NT EE A GS I TL TT LT 
