Abstract
Seasonal occurrences of citrus flat-headed borer, Agrilus auriventris SAUNDERS were observed since 1962 to 1965 at Omura, Nagasaki Prefecture. Dead citrus trees which were attacked by the larvae of citrus flat-headed borer were put in outdoor cages during the spring of each year and numbers of emergent adults of the beetles were collected daily until the end of autumn. The numbers of emergent adults in every 5 days duration were shown in Fig. 1 (1962), Fig. 3 (1963), Fig. 5 (1964) and Fig. 6 (1965) with the mean temperature and rainfall of periods concerned. Seasonal variations of emergence of same species which were observed at two different stations of Nagasaki Prefecture in 1962 and 1963 were shown for comparison. And the data on emergence (begining of emergence, peak of emergence and the end of emergence) obtained at the various districts of Japan sach as Kumamoto, Wakayama, Nara and Nagasaki were shown in Table 2. It seems that the emergence of this species begins at the middle of May or the beginning of June and continues until the middle of October. The peak of emergence was seen in June or July and sometimes August or September. Generally, the emergent activity of citrus flat-headed borer was observed in the morning of fineday. But some of individuals emerged in cloudy or rainy day. The sex ratio of this species was nearly 1:1 in almost cases. And the seasonal and daily emergence of both sexes have shown similar tendencies.
