Europe, Asia
Tansy ragwort (Jacobaea vulgaris)
Eggs are small, oval-shaped, and off-white. Larvae can be up to 6 mm long. Pupal chambers are barrel-shaped and dark brown. Adults resemble house flies with reddish eyes, dark bodies, and slightly clouded wings that extend beyond their body. They are up to 6 mm long. The abdomen of males is narrower than that of females.
Adults emerge in spring when tansy ragwort is in the rosette to late bolting stage. Adults lay eggs in young flower buds in late spring and early summer. Hatching larvae burrow into flower buds and feed on developing seeds through three instars (one larva per seed head). Their feeding causes a frothy spittle to form. Final-instar larvae exit seed heads in late summer, leaving behind characteristic exit holes. Pupae overwinter within loose soil or plant litter. There is one generation per year.
Larvae may destroy some or all seeds within attacked seed heads. Seed consumption does not kill existing plants, but reduces seed production, which may help decrease the rate of spread of tansy ragwort populations.
Szucs, M., J. Littlefield, C.B. Randall, and J.E. Andreas. 2022. Tansy Ragwort 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-2022-21-TANSY RAGWORT-A. https://bugwoodcloud.org/resource/files/25374.pdf