Author Institution: Ohio Agricultural Experiment Station, Wooste

Polivka, J. B.

The Ohio Journal of Science

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THE SEASONAL BEHAVIOR OF THE JAPANESEBEETLE IN OHIOJ. B. POLIVKAOhio Agricultural Experiment Station, WoosterThe study of the seasonal behavior of the Japanese beetle, Popillia japonicaNewm., in Ohio began in 1942 in Cleveland, Youngstown, and North Salem. Itwas later extended to include the newer epidemic areas as they were found. Haw-ley (1944) reported that as the beetle moved north or south from the center ofinfestation in Philadelphia its habits and reactions have been found to change.Greater differences in behavior will probably be found as the infested area becomeslarger. This paper is intended to show the behavior of the insect in Ohio in anaverage year and the differences in its behavior between different areas in the State.During the 10-year period, from 1942 through 1951, population studies wereconducted in 2 to 12 locations in the State each year. For example, in 1943, 2areas were studied, 1 in Cuyahoga County and 1 in Guernsey County. In 1951,12 locations were studied, 4 in Cuyahoga County, 1 in Lake County, 1 in TrumbullCounty, 1 in Columbiana County, 2 in Jefferson County, 1 in Guernsey County,and 2 in Washington County. The number of locations surveyed changed fromyear to year due to the flunctuation in the soil population in the area selected forstudy thus making it necessary to discontinue the study in some areas before newones were found. Also, in some years the study had to be changed in order to haveit fit in with the overall Japanese beetle research program.The soil population was determined by examining soil samples and noting thenumber of individuals of each stage present. Each sample in the various locationsconsisted of (a) 100 specimens or (b) the number of specimens found in ten one-third square foot cores of soil. The samples were taken at weekly intervals.The data for the years from 1942 through 1951 have been compiled andaveraged in table 1 by 7-day intervals from April 2 to October 14 in order to deter-mine the approximate distribution of the various stages of the insect in an averageyear. A wide variation was obtained in the behavior of the insect during the 10-year period, but as years with ideal conditions for the development of the insectoffset those with unfavorable ones, the data presented in table 1 show what canbe expected in an average year.The data in table 1 show that a few third instar larvae of the previous year'soverwintering brood were found in the soil as late as October 14. This conditionwas especially common in the Cleveland area in 1943 and 1944 when there wasscant rainfall throughout the two summers. The soil was very dry early in the springand summer of both years. This was responsible, undoubtedly, for the delay inthe transformation of the larvae. In this and other areas a delay has been causedalso by the larvae becoming infected with the spores of the milky disease supposedlylate in May or early June. When this happens the transformation is or seems tobe delayed as much as a month or more without the usual death and decay oflarvae especially during seasons with a low rainfall.These data show also that on October 8 to 14 eighty-seven percent of the larvaewere in the third instar, eleven percent in the second instar, and less than onepercent in the first instar. On April 2 to 8 of the following year ninety-two percentwere in the third instar and approximately eight percent in the second instar. Inthe spring of 1951 a few first instar larvae were found in the Cleveland area duringthe period April 30 to May 6 and again during May 14 to 20. The survival offirst instar larvae may have been due to the mild weather that prevailed during theTHE OHIO JOURNAL OF SCIENCE 54(1): 59, January, 1954.60 J. B. POLIVKA Vol. LIVwinter of 1950-51. Throughout the whole winter period there was a heavy snowcover with very little frost in the ground. These data would indicate that somefirst instar larvae can survive the winter under such conditions.During the course of this study some deviation occurred from year to year inthe seasonal cycle from that shown in table 1. For example, in 1941 and 1942,ninety-seven percent of the larvae overwintered in the third instar, while in 1943and 1944 and again in 1950, the percent of third instar larvae going through thewinter period varied from 60 to 79 percent in the different locations.TABLE 1The average percent of the various stages of the Japanese beetle in the soil in the different locationsfor the period from 1942 through 1951.Date, ofJJ/XdApr.Apr.MayMayJuneJuneJulyJulyAug.Aug.Sept.Oct.2- 89-1516-2223-2930-May 67-1314-2021-2728-June 34-1011-1718-2425-July 12- 89-1516-2223-2930-Aug. 56-1213-1920-2627-Sept.23- 910-1617-2324-301- 78-14Number ofSpecimens2575837051387213221153083333233224876347234382474203921722372220220272319169121011636132812961593495714535OverwinteringInstars1 27.8.108.0.3 12.15.0.3 1411.5.7,110.7,1.6,7.86.3.71.0.2.1.1392.391.989.491.386.984.485.488.394.588.079.151.631.824.39.84.32.53.81.72.01.40.61.21.20.81.40.30.7Pupae Adults0419424225843200.4.7.3.2.0.5.6.3.6.5.8.20.30.45.120.531.511.73.24.03.82.20.80.90.10.2Eggs5.618.559.766.455.934.022.613.48.77.93.00.51.72.60.410.29.219.531.450.556.045.735.419.19.610.73.56.51.30.6Instars21.02.22.55.215.836.845.249.131.727.919.523.211.811.230001823545974668687.1.2.9.1.4.2.5.7.6.1.7.1In order to determine whether the seasonal behavior of Japanese beetle stagesin the soil varies in the different areas in Ohio, the State was divided into threesections later referred to as the southern, central and northern areas. The southernarea falls between 39° and 40° north latitude, the central area between 40° and 41°,and the northern area between 41° and 42°. The data collected in the variousareas on the seasonal cycle of the insect were compiled and averaged for the purposeof comparing the behavior of the species in the different sections.From the data in table 2 it can be seen that the pupae appear about 10 daysearlier in the southern area than in the central section and 14 days earlierthan in the northern section. The difference is only 6 and 9 days in the adultstage, 0 to 6 days in the egg stage, 2 to 3 days in the first instar larvae, and noNo. 1 JAPANESE BEETLE 61difference to a slight reversal in development in the second and third instar larvaein the northern area. Based upon "Hopkins bioclimatic law" the appearance ofthe various stages in the southern section should have been approximately 8 daysearlier than in the central and northern areas. No difference should be foundbetween the central and northern sections because the greater elevation in centralOhio would tend to compensate for the difference in latitude. The data presentedhere agree with the law fairly closely during the fore part of the year but thereseems to be some deviation from the expected result in the latter part of the year.During the period from 1942 through 1951, traps were operated near each ofthe soil population study sites in order to obtain more information regarding thebehavior of the adults during the summer. Ten traps were used in each locationand the number of locations varied from three to eleven in the State each year.ComparisonSouthernCentralNorthernTABLE 2of the average time of appearance of thesoil in the southern, central, andAreaPupa5-306- 96-13various stages of the Japanesenorthern areas in Ohio.Average Time of Appearance ofAdult6-206-266-29TABLE 3Instar1 27-3 7-19 8- 27-2 7-21 8-157-9 7-22 8- 1beetle in the38-238-278-18The average time of appearance of the first beetle taken in traps and the average peak of beetle flightin the southern, central, and northern areas in Ohio.Time of Greatest Number 50 Percent of TotalArea Appearance of of Beetles Taken Catch ReachedFirst Beetle During Week Ending Week EndingSouthern 6-23 7-17 7-21Central 6-25 7-24 7-25Northern 6-25 7-26 7-26All traps were set out during the first week in June and removed during the secondweek in September. The traps were checked once a week during the summerexcept for the period from June 15 to 30 when they were checked daily for thepurpose of determining the time the first beetle was taken in the traps.Results of these studies were summarized and averaged in table 3 to show theaverage time of the first appearance of the adult in the traps and the averagetime the peak of beetle flight occurred in the three different areas in the State.The peak of beetle flight was determined in two different ways. By the firstmethod, the peak was based upon the time the greatest number of beetles weretaken in traps for any one week and by the second method it was based uponthe time at which 50 percent of the total catch was taken. The data in table 3were compiled for the 10-year period by averaging the times of appearance of thefirst beetle taken in the traps and also the time of the peak of beetle flight.These data show that in an average year the beetles appear first in southernOhio. However, the difference between the southern section and the central and62 J. B. POLIVKA Vol. LIVnorthern sections amounts to only 2 days. Slightly greater differences occurbetween the sections in regards to the peak of beetle flight. When the peak isbased upon the greatest number of beetles taken in any one week, the differenceamounts to 7 days between southern and central sections, 9 days between thesouthern and northern sections, and only 2 days between the central and northernareas. When the peak is based upon 50 percent of the total catch, the differencebetween the southern area and the central area is only 4 days, between the southernand northern sections 5 days, and only 1 day between the central and northernsections.The 'first appearance of beetles in traps varied from June 17 to 28 in thesouthern section, from June 17 to July 5 in the central area, and from June 19 toJuly 3 in the northern section. The peak of beetle flight based upon the greatestnumber obtained in any one week varied from July 16 to August 6 in the southernsection, from July 4 to August 11 in the central section, and from July 5 to August14 in the northern section. When the peak of beetle flight was based upon 50percent of total number taken, the peak varied from July 15 to August 3 in thesouthern section, from July 4 to August 6 in the central section, and from July 9 toAugust 12 in the northern section.In summarizing the results of this study, the data indicate (1) that there areusually a few third instar larvae that are delayed in development and found presentin the succeeding generation, (2) the seasonal development of the insect beginsearlier in southern than in northern Ohio as shown by the earlier pupation andemergence, (3) development of the first, second, and third instar larvae proceedsat a more rapid rate in northern Ohio than in southern Ohio as shown by theaverage time of the first appearance of the various instars, and (4) the beetlesappear and attain the peak of flight a few days earlier in the southern area thanthey do in the northern.LITERATURE CITEDHawley, J. M. 1944. Notes on the biology of the Japanese beetle. U. S. Bur. Ent. PI. Quar.Publication E-615.Hopkins, A. D. 1920. The bioclimatic law. Jour. Wash. Acad. Sci., 10: 34-40.

The Seasonal Behavior of the Japanese Beetle in Ohio

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The Seasonal Behavior of the Japanese Beetle in Ohio

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