Post-harvest insect pest directory
Lentil bruchid
Scientific name: Bruchus signaticornis
- Order
- Coleoptera
- Classification
- Primary
- Incubation at 20 C
- 10-14 days
- Incubation at 30 C
- 5-7 days
Description
Bruchus signaticornis is a minute bruchid (2.8–3.5 mm), showing sexual size dimorphism (male smaller). The prothorax is short, widest near midlength; posteriorly the lateral margins are nearly parallel. The elytra are flattened and distinctly maculate, bearing several pale grey to white spots. The overall habitus is compact with a low dorsal profile. Larvae develop inside seeds; they are white, reniform grubs reaching about 3.5 mm at the final instar, immediately before pupation.
Detection
Key indicators of the lentil bruchid Bruchus signaticornis in stored grain:
- Circular emergence holes on lentil seeds with smooth, beveled edges.
- Fine, powdery frass and mealy seed dust accumulating in seams or discharge points.
- Hollowed, lightweight, or shriveled seeds; cotyledons partly to fully consumed; elevated proportion of broken kernels.
- Presence of bruchid adults within the lot or on nearby surfaces; activity often increases under warm conditions (no silk webbing, unlike moths).
- Off-odors (musty or rancid) arising from damaged seed tissues and secondary microflora.
Practical checks: sieve a representative sample to detect adults and fines, and backlight seeds to reveal internal larval feeding (“shadowing”). These signs justify prompt sanitation, cooling/aeration, and approved targeted control.
Damages
In stored lentils, this coleopteran pest is endophagous: after oviposition, the neonate larva bores into the seed and consumes the cotyledons from within. Each colonized seed is virtually hollowed out, causing severe weight loss, loss of nutritive value, and loss of germinability in seed lots. Development is concealed, with frass and exuviae retained inside the grain. Adults exit by cutting neat, circular emergence holes; these visible perforations are poorly tolerated in human food. The presence of live individuals in marketed lots is prohibited, and even low-level infestation downgrades quality via perforation, contamination with insect fragments, and increased fines/dockage. The net effect is near-total destruction of infested lentils and a high risk of rejection for human consumption.
Environment
Bruchus signaticornis favors grain storage sites—warehouses, silos, and granaries—where lentils are kept; it prospers in dry, low-light, temperate conditions with moderate humidity, ovipositing on seeds as larvae develop endophytically within kernels.
Infested products
Lentil and protein crops.
Life cycle
Lentil bruchid (Bruchus signaticornis) is a monophagous, monovoltine seed beetle. Females oviposit about 50–60 eggs on flowers and young, forming pods. Embryogenesis lasts roughly 10 days. Mobile neonate larvae then penetrate the pod and enter the seeds, becoming apodous, endophagous larvae. In temperate climates, development takes 6–8 weeks. Only one generation is produced per year, and the species is strictly confined to lentil, reflecting high host specificity.
Geographical distribution
World.
Similar species
Bruchus rufimanus: broad bean weevil.
Bruchus pisorum: pea weevil.
Bruchus loti: no widely used English common name; generally referred to simply as a seed beetle.
Bruchus affinis: lesser pea weevil.
Bruchus brachialis: vetch bruchid.