Abstract
A survey was carried out in Wakayama, on some factors attributed to the behaviour of the overwintered larvae of the mealy bug, Pseudococcus kraunhiae KUWANA at the time of dispersement to the buds of the Japanese persimmon, Diospyros kaki L., from their hibernation in the spring. One tree, plantation of which took a place in 1942, was selected in an orchard and the number of all the bugs, buds and twigs was counted. The frequency distributions of the number of the bugs per bud and the number of the bugs per twig were well represented by Polya-Eggenberger's distribution type. The parasitism of the bugs was significantly heavy on the apical buds. The number of the bugs and buds per twig increases proportionatelly with the length of the twigs, but the number of the bugs per bud did not increase.
When 20 or 40 twigs were sampled from the tree at random, average number of the bugs per bud or per twig did not differ from the results of the survey on all twigs of this tree, but the differences appeared on the type of frequency distribution of the number of the bugs per bud, on the number of the bugs per twig classified by its length, and on the number of the bugs per bud classified by its position on a twig.
The survival rate of the bugs until maturation, from April 18 to June 24, was significantly higher on apical buds than on other buds.
