Leaf-miner: Lower-surface circular mine, just a few mm in diameter. Upper surface wart-like, somewhat discoloured, opaque. Mine often on top of the midrib. Sometime several mines together, which may fuse. The larvae live of cell sap that oozes into the mine (Bladmineerders van Europa).

Larva: The larvae of flies are leg-less maggots without a head capsule (see examples). They never have thoracic or abdominal legs. They do not have chewing mouthparts, although they do have a characteristic cephalo-pharyngeal skeleton (see examples), usually visible internally through the body wall.

Young larvae are white, older ones pale orange (Bladmineerders van Europa).

Puparium: The puparia of flies are formed within the hardened last larval skin or puparium and as a result sheaths enclosing head appendages, wings and legs are not visible externally (see examples).

Comments: Monarthropalpus flavus is an uncommon problem in the UK but sometimes heavy infestations occur. This tiny fly deposits its eggs in the new leaves during late April - May. The larvae feed inside the foliage, causing a yellowish discoloration on the upper leaf surface. The lower leaf surface develops a slight swelling in the area affected by the larva's feeding. The yellow larvae are up to 3mm long and they feed inside the leaves during summer – winter before pupating within the mines in spring. Several mines can develop in a leaf and heavily damaged ones often drop off (Royal Horticultural Society).

Hosts in Great Britain and Ireland:

Hosts elsewhere:

)Time of year - mines: Currently unknown.

Time of year - adults:Adult: One generation per year; the larve hibernates in the gall, and pupates in spring (Bladmineerders van Europa).

Distribution in Great Britain and Ireland: Southern England including East Norfolk, North Wiltshire, Shropshire, and Stafforshire, (NBN Atlas). Recorded from Worcestershire (Stratford upon Avon) (Mark Wilson, pers. comm.)

Distribution elsewhere: Widespread in continental Europe including Andorra, Austria, Czech Republic, French mainland, Germany, Hungary, Italian mainland, Poland, Romania, Spanish mainland, Sweden, Switerland, The Netherlands, Ukraine, and Yugoslavia. Also recorded in Near East and Nearctic region (Fauna Europaea).

NBN Atlas links to known host species:

British and Irish Parasitoids in Britain and elsewhere: Currently unknown