GALL
One to three larvae live between the inner petals and the developing achene; the warts on the inner petals are enlarged and brightly coloured. The achene becomes malformed. The mature larve is lemon yellow. Multivoltine, pupation in the gall or in the soil.

HOST PLANTS ....
Rumex acetosella, conglomeratus, crispus, maritimus, obtusifolius, palustris, pulcher & subsp. woodsii, sanguineus.

[click below for photos]

- Willem N. Ellis: (2021) Plant Parasites of Europe^©

Reference: https://bladmineerders.nl/parasites/animalia/arthropoda/insecta/diptera/nematocera/cecidomyiidae/cecidomyiinae/cecidomyiidi/cecidomyiini/contarinia/contarinia-rumicis/