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.

Hormonal control of pupal coloration in the painted lady butterfly Vanessa cardui.

Pupae of the painted lady butterfly Vanessa cardui exhibit pupal color polyphenism consisting of white, dark and intermediate types. We investigated environmental factors affecting pupal coloration and the physiological mechanisms underlying the control of pupal color polyphenism in this species. Over 80% of larvae reared at 16 degrees C developed into pupae of dark types, whereas over 82% of larvae at 32 degrees C developed into pupae of white types irrespective of long/short-day photoperiod conditions. When mature larvae reared at 32 degrees C were ligatured between thoracic and abdominal parts at three different pharate pupal stages, all of the head-thoracic parts developed into white pupae regardless of pupal stage, but all abdominal parts ligatured at the early pharate pupal stage only developed into dark pupae. These results indicate that temperature during larval stages is an important element affecting pupal coloration as an environmental cue in V. cardui, and that a factor(s) inducing white pupae is released from head-thoracic parts under conditions of high temperature. Additionally, when ligatured abdomens destined to develop into dark pupae were treated with crude extracts prepared from the central nervous system, all of the ligatured abdomens developed into white pupae at a level dependent on dose and pupal stage. These results suggest that the factor inducing white pupae is a key molecule controlling pupal color polyphenism in V. cardui.