A jishin mushi resembled a regular beetle, just more massive. It had a blue-green carapace that concealed a set of four wings. It had two small wings near its head, which allowed it to maneuver, and two large wings behind these that provided propulsion. The two large wings were very powerful, moving so fast as to appear invisible and gave the jishin mushi great speed during flight.
Its head was dominated by a pair of large mandibles. They were jagged and were strong enough to lacerate and mash a humanoid-sized creature. From the top of a jishin mushi's head sprouted two large antennae that resembled antlers. They were covered in fine follicles and were the jishin mushi's main sensory organ. Their main sense was their sense of smell and it was sensitive enough to pick up a scent up to 100 yd (91 m) away. Above the mandibles were a pair of large eyes.
A jishin mushi was not aggressive and only engaged in combat when defending itself or hunting prey.
The primary weapon of a jishin mushi was its large mandibles. It used them to bite at targets as well as to grab them and drag back to their lair. The jishin mushi had trouble grasping onto a target with its mandibles, however, so to prevent a target from slipping free, it would repeatedly crush the target until either killed or rendered unconscious.
However, the jishin mushi's most deadly attack, and what earned it the name earthquake beetle, was its natural ability to create localized earthquakes with its body. The jishin mushi did so by repeatedly striking the ground with its abdomen, generating tremors that grew in intensity with each strike.
Jishin mushi made their lairs deep within a forest. The lairs were temporary and very simple, often used just for a single day. They could be found resting within the trunks of dead trees, in small crevasses or under large piles of rotting vegetation.
Jishin mushi were nocturnal and spent the entire night hunting for food. As carnivores, they ate any meat, but favored oxen over all other meats. They lived solitary lives and were very rarely encountered.