Popation usually takes place on the surface of trunk of a ailanthus-tree on which the larval life is completed. However, the popae are often found on the surface of electric pole or wall of house. There were two major peaks of distribution of cocoons, and they occured at about the same height on each surface of ailanthus-tree and electric pole. Analyses of variance showed that the differences in the number of pupae between the surface-sections of trunk were insignificant. The biological observations on the larval stages of Parallelia arctotaenia GUENEE were carried out from 1960 to 1961 in Kyoto. Populations of this moty throughout the rose fields and gardens of Kinki district have become increased since 1958. The results of research are as follows: (1)Female moths lay eggs singly on the underside of young leaves. (2) Young larvae to 2nd instar feed on the underside of leaves, remaining the upper cuticle, and rest near the feeding places or on the main veins and petioles of leaves. Older larvae, however, eat through the leaf, mostly remaining the main vein and rest on the stems in the shade by days. Mature larvae make cocons and pupate in the soil or under the fallen leaves. (3) The majority of larvae have 5 moultings while oassing through 6 instars, but in male rarely 5 instars. Larval duration is about 17 days (Table 1). (4) From the day of hatching the largest width of head capsule of each larva was measured once a day with ocular micrometer (Table 2). It is possible to determine the instar of a larva by the measurement of the head width. (5) Larvae eat about 20 leaves to complete their development and the greatest amount of food was consumed by the last larval instar (Table 3). The relation between the larval instar (x) and the feeding area of leaf (y) is shown by the following formula: log y=0.84+0.56x. (6) Three to four generations occur in a year; hibernation in the pupal stage. Some puparia of 3rd generation overwintered and gave rise to adults in the following May-June (Table 4).
