Europe
Common St. Johnswort (Hypericum perforatum)
Eggs are elongated and pale red in color. Larvae are orange and can be up to 2 mm long. Pupae are a yellowish-red, becoming darker red as they mature. Adults are very small (3 mm long) and have dark red bodies with gray heads, wings, and legs. They have fine, delicate legs and antennae.
Larvae emerge in early spring and feed on common St. Johnswort leaf buds, causing leaves to grow into a spherical gall that is green with reddish markings. Larvae feed through three instars inside at the base of the gall. Several larvae are often found within one gall, and pupation also occurs inside the gall. Adults are sexually mature upon emergence and live for up to five days. There may be up to seven generations per year, though there are usually fewer than five. Larvae and pupae overwinter inside galls.
In suitable habitats, this insect can cause a loss of vigor and reduction of both root and foliage development. Heavily attacked plants are unable to obtain moisture and frequently die during drier seasons.
Randall, C.B., J.E. Andreas, J. Milan, and C.E. Moffat. 2024. Common St. Johnswort 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-2024-18-COMMON ST JOHNSWORT-A. https://bugwoodcloud.org/resource/files/33586.pdf