Europe and the Middle East
Primarily spotted knapweed (Centaurea stoebe subsp. micranthos), but also the meadow knapweed complex (Centaurea ×moncktonii complex) and diffuse knapweed (C. diffusa)
This species is very similar to Larinus minutus. Eggs are elongate, yellow, and often clustered in the flower head between pappus hairs. Larvae are white, C-shaped, and have brown head capsules. They are approximately 8 mm long. Pupae are 6 mm long and white, turning brown shortly before emergence. Adults are 4–5 mm long, a mottled-brown color, and have a large, bent snout.
Overwintering adults emerge from plant litter throughout the summer, feeding on knapweed foliage and flowers prior to laying eggs. Eggs are deposited in the flower head between pappus hairs. Larvae hatch in three days and feed on pappus hairs and developing seeds. Larvae feed through the entire knapweed flowering period, and develop through three instars in 3–4 weeks. The number of larvae per flower head depends on flower head size and knapweed species. Pupation occurs in nine days in pupal chambers made of chewed seeds and pappus hairs within the flower head. New adults emerge in late summer by chewing their way out, leaving behind the now-open pupal chamber. They feed on foliage and senescing florets before moving to overwintering sites at the base of plants. There is one generation per year.
Defoliation by adults can be severe, though the levels to which this negatively impact plant function remain unknown. Larval feeding consumes large portions of developing seeds, reducing the rate of knapweed spread.
Randall, C.B., J.E., Andreas, and J. Milan. 2023. Knapweed Biocontrol Agents: History and Ecology in North America. In: R.L. Winston, Ed. Biological Control of Weeds in North America. North American Invasive Species Management Association, Milwaukee, WI. NAISMA-BCW-2023-34-KNAPWEEDS-A. https://bugwoodcloud.org/resource/files/27451.pdf