Lesser Knapweed Flower Weevil

Larinus minutus is a species of true weevil known as the lesser knapweed flower weevil. It is used as an agent of biological pest control against noxious knapweeds, especially diffuse knapweed (Centaurea diffusa) and spotted knapweed.

The adult weevil is dark mottled brown with a long snout. It is 4 or 5 millimetres (0.16 or 0.20 in) long in total. It is active throughout the summer with a 14-week maximum adult lifespan. During this time the female lays up to 130 eggs, depositing them in the knapweed flower head. The larva emerges and burrows into the flower head where it feeds on the developing seeds. The larva damages the plant by reducing seed production (all of the seeds of diffuse knapweed and 25–100% of spotted knapweed) and the adult does damage by defoliating the plant as it feeds on the leaves prior to flowering. After flowering, adult weevils switch to feeding on flowers.