Europe, the Mediterranean
Yellow starthistle (Centaurea solstitialis)
Eggs are oval, smooth, and a translucent light yellow at first, turning darker with age. Larvae are creamy white with dark brown head capsules and are typically less than 3 mm long. Adults are small (2–2½ mm long), teardrop shaped, and have long curved snouts. They are black with blue-green metallic elytra and black to reddish legs. Males have an enlargement on the protibia which females lack.
Overwintering adults emerge in early spring and feed on yellow starthistle rosette leaves. Eggs are deposited singly inside the midrib or blade of rosette leaves. Hatching larvae tunnel down the leaf midrib into the root crown, feeding on plant tissue and developing through three instars. Pupation occurs in the root crown in late spring/early summer. Adults emerge in early summer and feed on leaves for about two weeks, then they leave the plant to overwinter in sheltered areas. There is only one generation per year. Multiple larvae have been found feeding within the same plant.
Adults feeding on yellow starthistle foliage leave characteristic feeding windows in leaf blades. Adult damage is typically superficial and does not do any appreciable damage. Heavy larval feeding can result in stunted plant growth and a reduction in seed production.
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