Silver-washed Fritillary (Argynnis paphia) – Wildlife of Japan
Introduction
The Silver-washed Fritillary, known in Japan as the “Midori-hyoumon,” is a common woodland butterfly found from Hokkaido to Kyushu. In summer it glides along sunny forest edges and woodland paths. Because of its bright orange wings and green-tinted underside, you can easily recognize this species even during a brief walk in the woods.
Appearance
This species has orange upperwings with dark spots, giving it the typical fritillary pattern. In addition, males show narrow scent lines on the forewings, while females lack these marks and look slightly plainer. The underside of the hindwing is yellow-green with pale, washed bands, and this combination of colors explains both its English and Japanese names.
Habitat & Distribution
In Japan the Silver-washed Fritillary lives mainly in forests, forest edges, and wooded paths. It occurs across the four main islands—Hokkaido, Honshu, Shikoku, and Kyushu. However, it does not extend into the southern Nansei Islands, where the climate and butterfly fauna are more subtropical.
Behavior
Adults are strong, smooth fliers that often patrol forest roads and glide between trees. They regularly stop at flowers or damp ground to feed. As a rule, the flight season runs from early summer to early autumn, although timing shifts slightly with altitude and latitude.
Diet
Caterpillars feed on violets (Viola spp.) growing in shaded woodland. Because these plants form patches on the forest floor, the species tends to follow them. Adults, on the other hand, visit a variety of flowers for nectar along forest margins and clearings.
Reproduction
The Silver-washed Fritillary produces one generation per year. Females lay eggs near violet plants rather than directly on the leaves. After hatching, the young larvae overwinter and then resume feeding in spring before they pupate and emerge as adults.
Conservation
At present the species remains common in Japan, and national conservation lists do not treat it as threatened. Even so, local declines can appear where woodland understory is cleared and patches of violets disappear. For this reason, maintaining semi-natural forest with a rich ground layer helps support stable populations.
Author’s Impression
I often see this species visiting the purple flowers of thistles. Sometimes several individuals gather on a single bloom, and as a result the flower head seems to glow with moving orange wings. It is a lively and memorable sight in the summer forest.
