Population dynamics of the chestnut gall-wasp,Dryocosmus kuriphilus Yasumatsu (Hymenoptera: Cynipidae) IV. Further analysis of the distribution of eggs and young larvae in buds using the truncated negative binomial series

Summary

Distribution pattern of eggs and the first instar larvae of the chestnut gall-wasp,Dryocosmus kuriphilus, per bud of the chestnut tree was re-examined using the truncatedPoisson and the truncated negative binomial series. The results are as follows:

• (1) About sixty percent of the distribution are approximated by the truncated negative binomial and another thirty percent by the truncatedPoisson. When the distribution has been approximated by the truncated negative binomial, the$\hat ks$ show scattered values, some of which are near thePoisson, but the mean value of$\hat k$ is about 4 both in eggs and in the first instar larvae.

• (2) The number of buds which have not been infested by gall-wasps is resulted from various factors as follows: (a) Buds formed after the laying activity of gall-wasps has ceased; (b) Old and shrunk buds which were avoided in laying; (c) Buds in which eggs have died by the time of sampling; and (d) Buds escaping ovipositions by chance. Most of the gall-wasp-free buds located in the middle part of the shoot are accounted for the zero-class expected by the negative binomial series.

• (3) Brass (1958) moment method for estimating parameters of the truncated negative binomial give good precision within the range of$\hat k$ from 1 to 10 and of$\hat \lambda$ from 1 to 6.

• (4) It is concluded that the truncated distributions used are useful for the purpose of analysis of the distribution pattern of the chestnut gall-wasp.