Abstract
We have known that the gypsy moth (Lymantria dispar LINNE) and the camphor silk moth (Dictyoploca japonica BUTLER) are the most important defoliator of the broad leaf stand and sometimes the former gives the greatest damage to all broad leaf forests and some needle leaf forests, the latter gives some damage to the japanese chestnut tree (Castanea crenata S. et Z.) in Japan.
In this report, the author deals with the results of the individual breeding of the gypsy moth and the camphor silk moth that feed on Quercus acutissime CARR. (the former) and Castanea crenata S. et Z. (the latter). These investigations were conducted from 1955 to 1957, and the gypsy moth was bred in 1956 and 1957, the camphor silk moth in 1955.
In order to know the correlation between the feeding quantity and the amount of the frass, the author measured the feeding broad leaf area, its dry weight and the dry weight of the frass on twenty individuals every year.
The results obtained from the investigations were as follows:
1) The gypsy moth hatched out from late in March to the middle of April and after the passing of the larval stage of about seventy days they pupated late in June. The pupal stage was about 11_??_15 days. Meanwhile, the camphor silk moth hatched out in April and began to pupation immediately after the larval stage of about sixty days. Its pupal stage was about one-hundred days and the emergence began at late in September.
2) The total feeding leaf area at the larval stage was 700_??_1, 100 cm2 at male and 1, 100_??_1, 800cm2 at female (gypsy moth), and 2, 000_??_3, 300cm2 at male and 2, 700_??_4, 000cm2 at female (camphor silk moth). That is, its feeding leaf area was very various at male and female.
3) The feeding quantity at the last instar was the greatest, namely, in comparison with the total, it amounted to about 60_??_70% at the gypsy moth, about 70_??_80%, at the camphor silk moth.
4) The total number of the frass evacuated at the larval stage was counted about 1, 500 at the gypsy moth, about 1, 700 at the camphor silk moth on an average, and its difference between male and female was not evident at the total number.
5) The correlations between the feeding quantity and the amount of the frass were shown with the straight line on the logarithms, that is; gypsy moth:logW=0.8297logD+0.01225 logW'=0.8681logD+0.60078 camphor silk moth: logW=0.8786logD-0.19007 logW'=0.9341logD+0.34470
W: the leaf area of Quercus acutissima CARR. and Castanea crenata S. et Z. in cm2
W': the dry weight of Quercus and Castanea in mg
D: the dry weight of the frass in mg
These correlations could be applied to the dead individual on the larval stage, male and femals as well as the case of the pine caterpillar.
