Common Tiger (Danaus genutia) – Wildlife of Japan

Introduction

The Common Tiger is an orange-and-black milkweed butterfly found only in the far south of the Ryukyu Islands. It glides slowly along sunny roadsides, making it easy to spot. However, it closely resembles the Plain Tiger (Danaus chrysippus), so observers need to check the wing pattern carefully.

Appearance

This butterfly has a wingspan of about 7–8 cm. Its wings are deep orange-brown with clear black veins that create a tiger-like pattern. Black margins with white spots frame the wings, and the forewing tips show a pale band. The underside looks similar but slightly lighter. In addition, males carry a narrow black scent patch on the hindwing, while females do not.

Habitat & Distribution

The Common Tiger lives across tropical and subtropical Asia. In Japan, people most often see it in the southern Ryukyu Islands, especially the Sakishima Islands such as Ishigaki and Iriomote. Reports also exist from nearby islands, although researchers are still refining its exact breeding range.
Within these warm areas, the butterfly uses open habitats—coastal scrub, field edges, roadside flowers and village margins. Occasionally, individuals appear farther north, but they do not form stable populations.

Behavior

The Common Tiger often glides gently along paths and roadsides. It frequently stops at flowers, especially during warm and sunny hours. Because the southern islands stay warm for much of the year, adults appear in many months. Its bright colours warn predators, as toxins from its host plants make the butterfly unpleasant to eat.

Diet

Adult butterflies feed on nectar from many flowers, especially roadside composites such as Bidens. In the larval stage, the caterpillars feed on climbing milkweed relatives in the dogbane family (Apocynaceae, Asclepiadoideae). Several native vines in this group serve as important host plants in the Ryukyu Islands.

Reproduction

Females place eggs one by one on young leaves and shoots of host plants. The caterpillars show black, white and yellow stripes and carry small flexible filaments at both ends. As they mature, they form a smooth, jade-green chrysalis decorated with metallic gold spots. Thanks to the warm climate, the species produces multiple generations each year.

Conservation

The Common Tiger remains widespread across Asia and faces no major threat. It also has no special conservation status in Japan. Even so, the butterfly depends on native milkweed vines and flower-rich open spaces. As a result, development and herbicide use may reduce local numbers. Protecting natural roadside vegetation and coastal scrub helps maintain the species.

Author’s Impression

Its calm, drifting flight brings a strong sense of the southern islands. Watching it settle on roadside flowers felt memorable, and the vivid contrast of orange and black stood out beautifully against the greenery.