Elephant darkling beetle

Elephant darkling beetle, Gnatocerus cornutus (F.), displays marked sexual dimorphism. In both sexes the integument is lustrous reddish‑brown. Males possess enlarged, horn‑like mandibular processes—cornute mandibles projecting forward from the head capsule—forming a conspicuous mandibular armature. Females lack these modifications: their mandibles are unarmed and comparatively short. The overall habitus is sleek and polished, emphasizing the species’ shining cuticle.

This species is a secondary pest of stored cereals. Adults and larvae abrade the outer kernel layers, targeting protein- and starch-rich tissues—bran/pericarp, aleurone, and germ. Feeding results in superficial gnawing, shallow peripheral pits, edge nibbling, and the production of fine frass, leaving dusty kernels with thinned or chipped seed coats. The injury is non‑diagnostic and easily confused with damage from other secondary tenebrionids. Consequences include weight loss, quality downgrading, contamination with frass and cast exuviae, increased susceptibility to fissuring and mold, and reduced germination in seed lots. Infestations commonly exploit cracked or previously damaged kernels and propagate through accumulations of fines.

Gnatocerus cornutus (F.), the Elephant darkling beetle, is a secondary pest of stored cereals and milled products. Typical infestation signs include: - Unpleasant, musty–rancid odor emanating from the commodity (taint). - Accumulation of fine, dusty frass and siftings; caking/clumping of grain or flour and localized heating. - Visible life stages: adults 3–5 mm, reddish-brown and flattened; males with prominent head horns and enlarged mandibles. Larvae slender, cream‑yellow with a sclerotized brown head. - Feeding concentrated on cracked/damaged kernels and bran; increased fines and broken kernels near surfaces and in seams. - Exuviae (cast skins), fecal pellets, and beetle fragments in sievings, around machinery, and under bag stacks. - Secondary mold development and an overall decline in grain quality and hygiene. These signs indicate an active infestation and degraded commodity quality; prompt sanitation, stock rotation, and targeted control are recommended.

Gnatocerus cornutus (elephant darkling beetle) has a holometabolous life cycle. After mating, females oviposit among stored commodities. Eggs hatch into active, free‑moving larvae that traverse the commodity, feeding continuously as they go. Development proceeds through successive larval instars to a pupal stage, followed by adult emergence. Adults are long‑lived (about 7–12 months), feed, and are capable of flight, aiding dispersal within and between storage sites. This species is partly predatory, opportunistically consuming dead or live insects and other animal proteins, which can enhance fecundity and population growth in infested facilities.

A synanthropic stored‑product beetle favoring heated indoor sites in flour mills and warehouses where flour, feed, and animal‑origin commodities are stored; it survives winter only in heated premises.

Species of the genus Tribolium. Long-headed flour beetle (Latheticus oryzae). Small-eyed flour beetle (Palorus ratzeburgii).