キタテハ(Polygonia c-aureum)の季節型決定要因としての日長

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Two quite distinct seasonal forms, the summer form and autumn form, exit in adults of the butterfly, Polygonia c-aureum. Experiments were carried out to discover the factor(s) of their determination. When reared under a day length of 14 hours or above, larvae pupated to produce adults of the summer form regardless of temperature condition. Larvae submitted to a day length of 12 hours or below, produced adults of the autumn form regularly here again regardless of temperature. Among the group kept under 13 hours' day length throughout the larval and pupal period, emergence of adults of both summer and autumn forms occured, without formation of any intermediate forms. These results seem to indicate that the adult seasonal form of this butterfly is determined by the photoperiodic condition of the younger period. Long-day condition induces appearance of the summer form, while short-day determines that of the autumn form, the critical day length being around 13 hours. Other experiments showed the likelihood that this determination is made during the larval period, especially during the last two instars. Short-day condition with drastically changing length of the dark phase was not effective for the induction of autumn form. Insertion of 2 hours' dark phase in totalizing 14 hours' illumination (long day) did not influence the long-day effect. Further studies on the same lines are needed for the understanding of the photoperiodic reaction in this species. Observation of the ovarian development in adults of both forms demonstrated that the individual of the autumn form were in a state of imaginal diapause, where the ovarian development occurred only about one month after the emergence. This was considerably later than in individuals of the summer form in which ovaries were mature within a week. Mating and oviposition took place successfully, however, in such one-month-old adults of the autumn form. The eggs hatched normally, yielding normal adults. The life of the autumnform adults exceeded 6 months, in contrast to that of the summer form which never lasted more than one month. This fact again confirms the diapausing nature of the autumn form. It follows therefore that Polygonia c-aureum is one of the butterflies with a 'long-day type' development, to which Vanessa (=Nymphalis) io (Danilevsky, 1961) is known to belong. Its mode of seasonal form determination is quite different from the case of Araschnia levana (Muller, 1955) where the form of adult is determined immediately by the diapausing or non-diapausing nature of the pupa which, in turn, is determined by the photoperiodic condition during the larval life. In polygonia, no pupa is diapausing, and the diapause seems to be inseparably bound to the seasonal form of the adult.
社団法人日本動物学会の論文
1963-03-15

キタテハ(Polygonia c-aureum)の季節型決定要因としての日長

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