Seasonal form and Mating behavior in the Asian Comma Butterfly (Polygonia c-aureum): Influence of Adult Diapause

Authors: HIROYOSHI, SATOSHI - Tokyo University Of Agriculture & Technology; MITSUNAGA, TAKAYUKI - National Agriculture And Food Research Organization (NARO), Agricultrual Research Center; Reddy, Gadi

Submitted to: Journal of Insect Behavior
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/15/2026
Publication Date: 7/20/2026
Citation: Hiroyoshi, S., Mitsunaga, T., Reddy, G.V. 2026. Seasonal form and Mating behavior in the Asian Comma Butterfly (Polygonia c-aureum): Influence of Adult Diapause. Journal of Insect Behavior. 39(23):1-14. https://doi.org/10.1007/s10905-026-09917-1.
DOI: https://doi.org/10.1007/s10905-026-09917-1

Interpretive Summary: A butterfly species displays two distinct seasonal forms—summer and autumn—that differ in wing shape, coloration, physiology, and reproductive timing; summer-form adults mate soon after emergence, while autumn-form adults typically enter diapause and postpone mating until spring, though some have been observed mating before winter. This study examined how seasonal form, age, photoperiod, and sex influence adult courtship, finding that summer-form males courted under all daylight conditions but rarely mated with autumn-form females, whereas autumn-form males courted both forms only under long-day conditions and showed minimal courtship under short-day conditions, except for a small subset that initiated courtship toward autumn-form females about 30 days after emergence, suggesting that some individuals may bypass diapause and mate before winter. Hormonal treatments with juvenile hormone (methoprene) or 20-hydroxyecdysone did not alter mating behavior, indicating that reproductive timing is governed primarily by photoperiod and seasonal form rather than endocrine stimulation. By clarifying how environmental cues regulate overwintering and off-season mating potential, this research strengthens USDA’s ability to anticipate and prevent invasive insect establishment, directly supporting the Secretary of Agriculture’s priority of safeguarding the integrity of American agriculture from biological threats.

Technical Abstract: A nymphalid butterfly, Polygonia c-aureum L. (Lepidoptera: Nymphalidae), has distinct seasonal diphenism, known as the summer form and the autumn form, which differ in wing morphology, color, behavior, and physiology. The summer form is non-diapause and begins reproduction shortly after emergence, whereas the autumn form induces adult diapause and reproduces in the spring after overwintering. However, autumn forms have been observed mating before overwintering in the wild, and it is unclear what causes this pre-overwinter mating. In this study, we aimed to clarify the relationship between seasonal form and mating by investigating the effects of photoperiod, age, seasonal form, and sex on courtship and mating behaviors during the adult stage. Summer form males courted females regardless of adult photoperiod (long or short days) or the female's seasonal form, but they rarely mated with autumn form females. Autumn form males courted females, both seasonal forms, under long-day conditions. Under short-day conditions, they rarely courted or mated with either autumn or summer form females. However, a small number (5.1%) of autumn form males showed courtship behavior toward autumn form females 30 days after emergence under short photoperiods. These results suggest that autumn forms may occasionally mate before overwintering. In addition, we also examined the effects of hormones on mating behavior because hormones are known to promote sexual maturation in several insects. Treatment with either the JH analog methoprene or 20-hydroxyecdysone had no detectable effect on mating behavior in this butterfly.