Western Conifer Seed Bug

• Its feeding punctures empty out pine seeds and have sharply cut pine nut harvests in some parts of the Mediterranean.
• In autumn it looks for somewhere to overwinter and gets into lofts, blinds and window frames by the thousand, though indoors it is entirely harmless.
• Its flattened, leaf-shaped hind legs make it unmistakable and are the reason for its common name.
• It is native to western North America and reached Europe in 1999, detected near Vicenza in northern Italy, probably in imported timber; within a few years it was in more than fifteen European countries.
• It pierces the cones with its stylet and empties the developing seeds; the external damage is almost invisible, but seed viability drops sharply.
• It buzzes loudly in flight and flies rather like a bumblebee; when disturbed it gives off a resinous smell.
• It can pierce cross-linked polyethylene pipes with its mouthparts and cause leaks.
• In autumn it comes into houses in large numbers looking for shelter, but it does not bite or damage the structure.

Skeleton type

Invertebrate - chitin exoskeleton (insect)

Habitat and environment

Pine woods and other conifer stands; it feeds on the seeds inside the cones and on the shoots, and overwinters as an adult in bark crevices or inside buildings

Size at birth

Barrel-shaped egg of about 2 mm; the early-instar nymphs are red or orange with dark legs

Sexual maturity

The overwintering adults become active again in mid-March and lay in spring; one to two generations a year are recorded in Europe, and up to four depending on the locality

Gestation / incubation

The eggs hatch in about 10 days; the nymphs go through five instars and reach adulthood by midsummer

Litter / clutch size

Rows of 10 to 50 barrel-shaped eggs, glued one after another onto conifer needles; up to about 80 eggs per female per season are reported

Sources consulted: Wikipedia (es): Leptoglossus occidentalis · Ficha de especie de Leptoglossus occidentalis · Forest Pests Europe · Museum Pests, ficha Western conifer seed bug · observaciones del Pacifico Noroeste · Fichas de manejo de Leptoglossus occidentalis · Barta, desarrollo y supervivencia invernal de L. occidentalis en Eslovaquia

Best time: Autumn, when it seeks shelter and comes into houses