Europe, Western Asia, the Mediterranean
Yellow starthistle (Centaurea solstitialis)
Eggs are tiny, yellow, and elongate. Larvae are up to 6 mm long with white, C-shaped bodies and brown head capsules. Pupae are typically creamy white with obvious appendages and a medium-length snout. Adults are 5–6 mm long with oval-shaped bodies and medium-length snouts. Adult bodies are brown with white hairs that give them a mottled appearance. The body hairs are often yellowish from yellow starthistle pollen.
Overwintering adults emerge in summer when yellow starthistle is in bud and flowering, and they feed on florets and pollen. Females lay eggs singly in open flower heads at the base of florets. Larvae hatch in summer and feed on developing seeds through three instars. Pupation occurs in seed heads in chambers made of damaged seed and receptacle tissue. Adults emerge in late summer and overwinter in the soil litter. There is one generation per year.
Adults feed on pollen and florets, though the impact is typically minor. Larvae feed on flower head tissue and developing seeds. Seed consumption does not kill existing plants, but reduces seed production which may help decrease the rate of spread of yellow starthistle populations and may reduce infestations in some habitats.
Randall, C.B., L. Smith, and J. Milan. 2023. Yellow Starthistle 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-2023-14-YELLOW STARTHISTLE-A. https://bugwoodcloud.org/resource/files/27955.pdf