Hylotrupes bajulus can reach a body length of about 8–20 mm (0.31–0.79 in), while mature larva can reach 30 mm (1.2 in).
These beetles  are brown to black, appearing grey because of a fine grey furriness on most of the upper surface.
On the pronotum two conspicuously hairless tubercles are characteristic of the species.
On the elytra usually there are two whitish pubescent spots.
Females do not have a real ovipositor, only a little more elongated telson.
The species can be defined polymorphic, having an extreme variability, both in the dimensions and in the aspect.
In small specimens the pubescent spots on the elytra disappear almost completely and the legs and antennae turn to a reddish color.
Hylotrupes bajulus can reach a body length of about 8–20 mm (0.31–0.79 in), while mature larva can reach 30 mm (1.2 in). These beetles  are brown to black, appearing grey because of a fine grey furriness on most of the upper surface. On the pronotum two conspicuously hairless tubercles are characteristic of the species. On the elytra usually there are two whitish pubescent spots. Females do not have a real ovipositor, only a little more elongated telson. The species can be defined polymorphic, having an extreme variability, both in the dimensions and in the aspect. In small specimens the pubescent spots on the elytra disappear almost completely and the legs and antennae turn to a reddish color.
Hylotrupes