Blue Admiral (Kaniska canace) – Wildlife of Japan

Introduction

The Blue Admiral is a striking butterfly found in Japan.
It stands out for its dark wings crossed by a vivid blue band.

In forested environments, people most often encounter this species on tree trunks or near sap flows.
Unlike many butterflies, it rarely visits flowers.

Appearance

The adult Blue Admiral is a medium to large butterfly.

Its wings appear dark brown to black, while a bright blue band runs across both the forewings and hindwings.
In addition, small pale spots appear near the tips of the forewings.

When the butterfly closes its wings, the underside resembles tree bark or dead leaves.
As a result, the butterfly blends easily into its surroundings.

The proboscis shows a red color and becomes especially noticeable during feeding.

Habitat & Distribution

In Japan, the Blue Admiral mainly inhabits forests, woodland edges, and hilly or mountainous areas.
However, it may also appear near wooded green spaces.

Outside Japan, the species occurs across several parts of Asia.

Behavior

Adults often rest quietly on tree trunks, rocks, or the ground.
During these times, they remain still for long periods and can be easy to overlook.

In general, observers encounter this species more often in shaded forest environments than in open areas.

Diet

Adult Blue Admirals rarely visit flowers.
Instead, they mainly feed on tree sap and fermenting or rotting fruit.

Meanwhile, larvae feed on recorded host plants such as Smilax china, Tricyrtis species including Tricyrtis hirta, and lily species like Lilium lancifolium.

Reproduction

Females lay eggs on or near larval host plants.
In Japan, the Blue Admiral overwinters as an adult.

After winter, adults become active again as temperatures rise in spring.
Therefore, the number of generations per year varies by region and does not remain fixed nationwide.

Conservation

The Blue Admiral appears widely across Japan and does not face national-level threat status.
Nevertheless, the loss of forest habitats may affect local populations.

Author’s Impression

The Blue Admiral is a butterfly commonly seen in forests and mountainous areas.
It often rests with its wings fully open, as if basking in the sunlight.

When sunlight hits the wings, the blue band appears especially vivid and beautiful.
For this reason, seeing this butterfly quietly shining in a forest always leaves a strong impression.