This experiment was conducted to investigate the vriabibities of the pupal weight and the number of eggs in the ovary of the fall webworm, Hyphantria cunea Drury. collected from the seven different host plants in the field. The correlation between the pupal weight and the number of eggs in the ovary was studied in connection with the species of the host plants. The results obtained were as follows. I) The pupal eight was varied with the species of the host plants and sexes. The order of average female pupal weight was Populus euramericanal Guinier(206.6 mg). Juglans mandshurica Max. (J97.8 mg). Platanus orientalis L. (182.4 mg). Acer neugndo L. (172.2 mg). Taxodium distichum Rich. (172.1 mg). Salix babylonica L. (128.8 mg) and Prunus serrulata var. spontanea (Max). Wilson (103.4 mg). and of the average male pupal weight. T. distichum (125.2 mg). P. orientalis (123.5mg). J. mandshurica (114.4 mg). A. negundo (109.5 mg). Peuramericana (106.3mg). S. babylonica (94.3 mg). and P. serrulata var. spontanea(74.6 mg). The weight of female pupae was greater than that of male pupae in all case. 2) The unmber of eggs in the ovary was also vaied with the species of the host plants. The order of the average number of eggs in the ovary was P. euramericana(1331.1). J. mandshurica(I239.9). T. disichum (1237.0). A. negundo (1186.9). P. orientalis (1145.5), S. babylonica (800.0) and P. serrulata var. spontanea (641.5). 3) The number of eggs in the ovary for all the host plants tested was highly correlated with the pupal weight.