Changes of seasonal morph development induced by surgical operations in pupae of the large map butterfly Araschnia burejana Bermer (Lepidoptera: Nymphalidae).

The nymphalid butterfly Araschnia burejana and the papilionid butterfly Papilio xuthus exhibit seasonal diphenism comprising spring-morphs that develop from diapause pupae and summer-morphs that develop from non-diapause pupae. The development of seasonal morphs in A. burejana is regulated by the timing of secretion of ecdysteroids for adult development, whereas that in P. xuthus is regulated by the secretion of summer-morph-producing hormone, which is present in the brains and is under control of the photoperiod. We investigated whether a cerebral factor derived from brains plays a significant role in the regulation of seasonal morph development in A. burejana using surgical operations. Pairs of chilled diapause pupae that had been chilled for more than 3 months at 4°C were joined surgically to each other and then developed into spring-morph or spring-like-morph adults. Chilled diapause pupae that were joined with 1-day-old non-diapause pupae developed into summer-morph or summer-like-morph adults. When the brains of non-diapause pupae were removed surgically 6-8 hr after pupation with and without injection of 20-hydroxyecdysone, a large portion of them developed into spring-morph or spring-like-morph adults, respectively. Furthermore, 90% of non-diapause pupae developed into spring-morph or spring-like-morph adults when the neck was ligated within 5 min after pupation. These results indicated that a cerebral factor showing summer-morph-producing hormone activity, which is secreted from the brain in the early pupal stage, in addition to 20-hydroxyecdysone for adult development, play a significant role in the determination of summer-morph development in non-diapause pupae of A. burejana.

Diapause pupal color diphenism induced by temperature and humidity conditions in Byasa alcinous (Lepidoptera: Papilionidae).

We investigated whether diapause pupae of Byasa alcinous exhibit pupal color diphenism (or polyphenism) similar to the diapause pupal color polyphenism shown by Papilio xuthus. All diapause pupae of B. alcinous observed in the field during winter showed pupal coloration of a dark-brown type. When larvae were reared and allowed to reach pupation under short-day conditions at 18°C under a 60±5% relative humidity, diapause pupae exhibited pupal color types of brown (33%), light-brown (25%), yellowish-brown (21%), diapause light-yellow (14%) and diapause yellow (7%). When mature larvae reared at 18°C were transferred and allowed to reach pupation at 10°C and 25°C under a 60±5% relative humidity after a gut purge, the developmental ratio of brown and light-brown, yellowish-brown, and diapause light-yellow and diapause yellow types was 91.2, 8.8 and 0.0% at 10°C, and 12.2, 48.8 and 39.0% at 25°C, respectively. On the other hand, when mature larvae reared at 18°C were transferred and allowed to reach pupation at 10°C, 18°C and 25°C under an over 90% relative humidity after a gut purge, the developmental ratio of brown and light-brown, yellowish-brown, and diapause light-yellow and diapause yellow types was 79.8, 16.9 and 3.3% at 10°C, 14.5, 26.9 and 58.6% at 18°C, and 8.3, 21.2 and 70.5% at 25°C, respectively. These results indicate that diapause pupae of brown types are induced by lower temperature and humidity conditions, whereas yellow types are induced by higher temperature and humidity conditions. The findings of this study show that diapause pupae of B. alcinous exhibit pupal color diphenism comprising brown and diapause yellow types, and suggest that temperature and humidity experienced after a gut purge are the main factors that affect the diapause pupal coloration of B. alcinous as environmental cues.