Ornate trogoderma

Ornate trogoderma (Trogoderma ornatum) adults are small, oval beetles, 1.9–3.6 mm long. The dorsal surface is dark brown, with lighter brown maculation across the elytra, creating a mottled, ornate aspect. Larvae are oval and densely setose, bearing conspicuous terminal tufts of hairs on the last abdominal segment. Through development, larval coloration shifts progressively from yellowish-white to reddish-brown. The combination of patterned adults and shaggy, tuft-tailed larvae provides a clear, practical basis for identification.

In stored grain, injury is caused exclusively by the larval stage. Larvae are external feeders that rasp the pericarp and germ, preferentially attacking cracked, broken, or otherwise compromised kernels. Feeding results in superficial abrasions, embryo nibbling, and localized removal of endosperm near fissures, producing fine powdery frass. Consequences include slight weight loss, reduced test weight, diminished germination when the embryo is scarified, and quality downgrades. The principal commercial impact stems from contamination rather than dramatic kernel destruction: accumulations of frass, cast exuviae, and larval setae taint lots and trigger rejections. Adults do not feed on grain and cause no direct damage.

Signs of Ornate trogoderma in stored grain (Trogoderma ornatum (Say)): - Larval exuviae (cast skins) abundant in the lot, especially in fines and surface dust; light, tan‑brown, dorsally split skins retaining larval setae — a key diagnostic indicator. - Setal contamination: loose larval hairs (setae) mixed with grain and dust. - Live larvae: elongate, densely setose, often with posterior hair tufts, wandering on the grain surface and along seams. - Feeding traces: fine frass and powdering at “hot spots,” with fragments of seed coats and irregularly damaged/broken kernels. - Adults: small, oval dermestid beetles with patterned/scaled elytra, occasionally observed on the grain surface, walls, or near lights. - Aggregations in warm, dry niches (beneath spillage, in cracks, and under caked layers).

Trogoderma ornatum (Say) is a holometabolous dermestid. After emergence, adults disperse in storage, mate, and females oviposit directly among food sources, especially grain and associated residues. Eggs hatch to setose, wandering larvae—the primary trophic stage—which pass through multiple larval instars via ecdysis, feeding and contaminating product with frass and cast exuviae. If conditions are suboptimal (temperature or moisture), larvae can enter facultative diapause (dormancy), extending survival until development is favorable. At maturity, a prepupal larva forms a pupation site, typically within the last larval exuvia in the commodity. Teneral adults eclose, sclerotize, and seek mates; adults are relatively short-lived and may feed little. Development rate is temperature- and humidity-dependent, allowing overlapping generations in warm stores.

Xerophilic and synanthropic, Trogoderma ornatum thrives in dry, warm grain-storage sites—granaries, warehouses, elevators, and silos—especially in undisturbed residues, dust, and crevices around stored cereals and legumes.

Other species of the genus Trogoderma.