Abstract
Argas japonicus Yamaguti, Clifford and Tipton wintering in 2 Delichon urbica nests were collected at Agematsu, Nagano Prefecture, Japan, on November 17,1967. All the nymphs other than protonymphs were reared individually on chickens up to adults in the laboratory. Using the informations on the sex, retrospectively, following data were obtained. 1. The wintering population comprized 48 larvae (8.9%), 146 protonymphs (27.0%), 215 deutonymphs (39.7%), 10 tritonymphs (1.8%) and 122 adults (22.6%). 2. The sex ratios for the deuto- and tritonymphs and for the adult did not deviate significantly from half-and-half. 3. There was a very high regression of the idiosomal width toward the indiosomal length in the nymphal and adult stages. 4. The idiosomal lengths of the protonymph, deutonymph and adult were normally distributed, respectively. 5. Smaller sized deutonymphs oftener gave rise to tritonymphs in the laboratory. The difference by potential sex in the ratio of deutonymphs that passed through the 3rd instar nymphs was nonsignificant. 6. The idiosomal length of newly emerged ticks that were fed on chickens in the laboratory was described by the regression of the length of the preceeding stages. The regression coefficient was significantly larger in the female than in the male.
