Chinese bruchid (Chinese seed beetle)

Adults of the Chinese bruchid, Callosobruchus chinensis, are tiny seed beetles (3–4 mm) with a compact, subglobose, strongly convex habitus. Legs and antennae are conspicuously elongate. The elytra are variegated and abbreviated, leaving the terminal abdominal tergite (pygidium) exposed. Larvae are creamy white, C‑shaped, and practically apodous.

Damage is highly diagnostic in stored grain. Larvae develop endophytically within individual kernels, feeding internally and hollowing the seed contents. On emergence, adults cut a crisp, circular exit hole in the seed coat, leaving neatly perforated grains. In heavy infestations, intense respiration drives metabolic heating and moisture migration, creating hot spots that reduce commodity quality and promote mold growth. The result is downgrading and spoilage of infested lots.

Primary sign of infestation by the Chinese bruchid, Callosobruchus chinensis (L.), in stored grain is the presence of conspicuous, round adult emergence holes on the seed coat (testa). These clean‑edged, circular perforations are drilled as adults exit the seed and are highly characteristic and diagnostic of this species, making them readily visible indicators of infestation.

Chinese bruchid, Callosobruchus chinensis (L.), reproduces entirely on stored legumes. Adults are very active runners and swift fliers. Females oviposit, cementing single eggs to the external seed coat (testa). Upon eclosion, the 1st-instar larva immediately bores through the tegument and feeds endophagously inside the seed. Successive larval instars develop wholly within, consuming cotyledon and embryo. Before pupation, the final instar mills a circular emergence tunnel, leaving a thin “window” in the testa. Pupation occurs inside the seed. The teneral adult ecloses, completes sclerotization, and exits by breaking the window, leaving a characteristic round exit hole.

Callosobruchus chinensis favors warm, moderately humid post-harvest settings: granaries with dried pulses (beans, peas), enabling continuous generations via oviposition on seed. It also infests fields with host legumes; cool, dry climates limit development.

Bean weevil (Acanthoscelides obtectus), pea weevil (Bruchus pisorum), other species of the genus Callosobruchus.