Effect of larval brain extracts derived from three swallowtail butterflies, Papilio helenus L., P. machaon L. and P. memnon L., on seasonal morph development of P. xuthus L. (Lepidoptera: Papilionidae)

摘要

Adults of the three papilionid butterflies, Papilio helenusL., Papilio machaonL. and Papilio memnonL., exhibit seasonal diphenism comprising spring and summer morphs. To elucidate the physiological mechanism underlying seasonal morph development in papilionid butterflies, we investigated whether a cerebral factor showing summer-morph-producing hormone (SMPH) activity is present in the brain of three Papilio species using an assay system with chilled male short-day pupae of P.xuthusL. When 2% NaCl extracts derived from 20 larval brains of the three species were injected into abdomens of chilled male short-day pupae of P.xuthus, all recipients destined to develop into spring-morph adults developed into summer- and intermediate-morph adults. On the other hand, all recipients injected with distilled water as a control developed into spring-morph adults. These results indicate that a cerebral factor showing SMPH activity is present in the larval brain of the three Papilio species. Additionally, all recipients injected with 2% NaCl extracts derived from 20 adult brains of Bombyx moriL. also developed into summer- and intermediate-morph adults. The results revealed that SMPH or a cerebral factor showing SMPH activity is widely distributed among lepidopteran insects.