Some biological notes on Pseudoxenos iwatai Esaki : (II) Its biology and life history

The present paper deals with the biology and the life history of Pseudoxenos iwatai Esaki. 1. The longevity of the males which emerged from their puparia was very short, being 4-8 hours. Besides, the duration of the time was within one hour in which they could fly vigourously with opening their hind wings. From this, it is infered that mating is performed within this flying time. 2. The period of emergence of males was about sixteen to twenty days from the end of June to the middle of July in Fukuoka. 3. Of eight males examined, seven males emerged at 9 : 15-10 : 45 in the morning and one male at 2 : 45 in the afternoon, respectively (Table 1). As this time of emergence accords just with the time of flower-visiting activity of their host wasps, it is inferable that mating is achieved on the flowers in bloom. 4. According to investigation carried out in Ina districts, the male of P. iwatai emerged from its puparium inside the abdomen of host wasp, Rygchium micado Kirsch, ten days after the host emergence. It seems therefore that the pupal stage of male (including the prepupal stage) lasts about ten days. 5. The percentage of stylopism of P. iwatai on the male of R. micado was 27.3%, showing in its rate very high as compared with that on the other host wasps. P. iwatai prefers R. micado as its host rather than it does to the other host wasps. 6. The sex ratio of male P. iwatai to female one was 55 : 88, so far as it is concerned to the results obtained from the examination on three species of host wasps carried out in 1959 and 1960 in Fukuoka (Table 5). 7. Some of P. iwatai has two generations a year synchronizing with the generation of its host, R. micado, while the larger parts of this species has one generation a year. 8. The body wall of the female of P. iwatai is constructed with three integuments viz. the last larval skin, the pupal skin and the imaginal skin from the exterior to the interior, just as it is demonstrated in the two genera, Elenchus (Lindberg 1939) and Stylops (Ulrich 1930 and Lauterbauch 1956) (Fig. 1).