Europe and Northern Asia
Yellow-flowered invasive hawkweeds (Pilosella flagellaris) and orange hawkweed (P. aurantiaca)
Eggs are oval, elongated, and have a netted surface structure. They are white at first then turn gray if fertile. Larvae (maggots) are tan in color and with a few long hairs. Pupae are small and dark brown, and thus, very difficult to see in soil. Adults appear black from a distance, but when viewed up-close, are seen to be covered in short, fine, golden hairs. Adults can be 6–7 mm long, including their translucent-brownish wings.
Adults emerge from May through June, with males appearing before females. A mating ritual occurs in small forest meadows where the male flies high in the air before descending to land close to the female sitting on low vegetation. Because of the need for open space during mating, full generations of C. urbana cannot be reared indoors. Females deposit eggs at the base of rosette leaves. Larvae soon emerge and live in the soil, feeding externally on hawkweed roots throughout the growing season. They develop through three instars. In fall, third-instar larvae pupate in the soil, and pupae overwinter just beneath the soil surface. There is one generation per year.
Larval feeding reduces both above- and below-ground biomass as well as seed production. Larval feeding may also make plants more susceptible to secondary attack by pathogens.
De Clerck-Floate, R.A., J. Littlefield, G. Cortat., and C.E. Moffat. 2023. Hawkweed 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-2023-36-HAWKWEEDS-A. https://bugwoodcloud.org/resource/files/29157.pdf