INSECT PEST SURVEY BULLETIN 
Vol. 21 Supplement to No. 9 December 15, 1941 
THE FIELD STATUS OP PARASITES OF THE EUROPEAN CORN BORER. 
AT THE CLOSE OE TEE 1940 SEASON 
By V. G. Bradley and C, A. Clark, asso ciate entomologists . 
Division of Cereal end Forage Insect Investigations 
Bu rec u of Entom o logy and Plant Quarantine 
United Soates Department of Agriculture 
In the fall of 1940, immedia.tely subsequent to the establishment of 
seasonal equilibrium in the relationship between host and parasite, surveys 
were conducted to obtain information on the current status of parasites of 
the European corn borer. No attempt was made to randomize the location of 
sampling points over the entire area infested by the corn borer, because con- 
tinuous observations throughout the years following the colonization of para- 
sites have been such as to provide adequately reliable information on their 
dispersion characteri sties. Commensurate with funds available, the areas sur- 
veyed were selected, therefore, with a view to obtsi ning- the maximum informa- 
tion pertaining to (l) the fluctuations of parasite abundance at representative 
colony sites where dispersion restrictions had been determined previously, 
(2) abundance status, coupled with directional dispersion tendency and the 
extent of dispersion in areas where the parasites were .still in the process 
of dissemination, (3) a qualitative and quantitative analysis of the parasite 
complex in both types of areas, (4) establishment of parasites at sample disv 
persion colony sites. With the data thus obtained for the current season, 
supplemented by the results of investigations in previous years, data are 
available to permit a close interpretation of the status of parasites through- 
out the entire infested area. 
Collections of ectophagous parasites and the puparial remains of those 
which issued from their host and emerged prior to the time of collection, to- 
gether with living borers which might harbor endophagous forms, were made at 
16 points* The size and number of collections taken at each locality and the 
design utilized to locate the sampling point were determined by the type of 
information desired and the status of the introduced parasites prior to 1940 
in the area to be surveyed. Host and parasite material from the Lake States 
(including the western portions of New York and Pennsylvania) and the Eastern 
States area were handled at the corn borer laboratories at Toledo, Ohio, and 
Moorestown, N. J., respectively. The results of observations in both areas 
are summarized in tables 1 and 2, 
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