Japanese Earth-boring Dung Beetle (Phelotrupes auratus) in Japan

Introduction

The Japanese earth-boring dung beetle (Phelotrupes auratus) is a striking beetle native to East Asia, including Japan. It belongs to the family Geotrupidae, a group known for digging tunnels underground. With its glossy metallic body, this beetle plays an important but often unseen role in maintaining the health of forest ecosystems by burying animal droppings.

Appearance

Adults are typically 15–21 mm long, with a robust, oval body that is strongly convex. The head is slightly extended at the front, the pronotum has a distinct groove running down the center, and the elytra show pronounced vertical striae—features that give the beetle a tough, armored look.

Its metallic colors are the highlight: individuals may appear golden-green, vivid blue, or even purple depending on the region. This variation makes the species especially popular among insect enthusiasts in Japan.

Habitat & Distribution

Phelotrupes auratus is widely found in forests across Japan and in parts of East Asia. It inhabits soil-rich woodland environments where animal dung is available, helping sustain the species and its ecological role.

Behavior

Most of its life is spent near or beneath the surface of the forest floor. When a beetle locates fresh dung, it digs tunnels beneath or beside it using its strong forelegs. Small pieces of dung are buried underground, where they remain protected from drying out or being taken by other animals. If you watch quietly, you may see one working with surprising determination.

Diet

This beetle is coprophagous, feeding mainly on mammal dung. Both adults and larvae rely on this buried resource. By removing dung from the ground surface and incorporating it into the soil, the species contributes to cleaner forest floors and natural nutrient cycling.

Reproduction

Phelotrupes auratus undergoes complete metamorphosis: egg, larva, pupa, and adult. Eggs are laid near the buried dung, which serves as the sole food for larvae. The larvae are typical C-shaped grubs with pale bodies and hardened brown heads, adapted to a life spent underground.

Conservation

This species remains common where healthy forest conditions and wild mammals are present. Its population stability depends on the availability of dung and undisturbed soil environments. Conserving forest ecosystems therefore directly supports the ecological services that this dung beetle provides.

Author’s Impression

Although feeding on dung may seem unappealing at first, the beauty of this beetle tells another story. Its jewel-like metallic sheen and regionally varied colors make it especially popular among Japanese insect fans. If you come across animal droppings in a Japanese forest, take a closer look—one of these brilliant underground workers might be nearby.