The quadrat census for the adult population of Epilachna vgintioctomaculata tended to underestimate its true density, because this insect often dropped onto the ground in response to a slight disturbance. While, the marking-and-recapture method was proved to be applicable when the individual insects were marked and released in the same place where they were caught. By using a modified method of BAILBY's triple catch as discribed here, the population estimates on successive occasions could be obtained from a single release of marked insects on a given date and the recapture data on several subsequent dates, if each marked individual was identifiable by its specific mark. The death-rate of overwintered adults after their arrival to the potato field from the hibernation site was kept at a relatively low level until mid June, and then it increased rapidly. Overwintered adults died out by early July, at which time the next generation insects emerged as adult. From the data for the marked insects, it was also indicated that overwintered adults rarely moved across the foodless space after they settled on a potato field, and that their movement within a single field was also limited to a small extent.
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