Leaf-mine: An initially narrow linear mine which after the first moult widens into large linear or irregular blotch; frass in distinct rows in the early linear section, later more scattered (Spencer, 1976: 128-9, fig. 221).

The mine is described by Hering (1957a) as follows: Upper-surface mine. The start is corridor-like and generally follows the leaf margin. Further on the mine widens considerably, forms a secondary blotch and gets irregular sides that are deeply eaten out. Primary and secondary feeding lines clearly visible. Frass mostly in large clumps. Pupation outside the mine. The mine only rarely occurs in Geranium robertianum; the frass then is fine-grained and the mines are smaller. Hering didn't think it impossible the the miners of Geranium robertianum and the other Geranium species might be a different species. Dutch material might form a different third species (Bladmineerders van Europa).

The first instar larva makes an initial corridor, with frass in two lines. Then a large irregular blotch is formed (British leafminers).

Larva: The larva is illustrated in Bladmineerders van Europa.

Puparium: Reddish-brown; posterior spiracles each with 3 bulbs (Spencer, 1976: 128). The puparium is illustrated in Bladmineerders van Europe.

Agromyza nigrescens puparium Image: Willem Ellis (Bladmineerders van Europa)

Hosts in Britain:

Hosts elsewhere:

Time of year - mines: September.

Time of year - adults: Unknown.

Distribution in Great Britain and Ireland: Widespread in Britain including Middlesex (Greenford) (British leafminers), Surrey (Kew), Yorkshire (Gorsdale Scar), Cardiff, Edinburgh (Spencer, 1972: 41), Warwickshire (The Bogs) (Robbins, 1991: 38) and Cambridgeshire, Cardiganshire, East Norfolk, East Suffolk, Glamorgan, North Somerset, West Kent, West Norfolk, West Suffolk and Westmorland (NBN Gateway - N.B. includes Watsonian Vice Counties having publicly available records that fall within or overlap the vice county border at 10km resolution or better i.e. a record for a vice county may relate to an adjacent vice county - for included datasets see NBN Grid map below).

NBN Grid map: Note that not all datasets on the NBN Gateway may be available on the map below. If you are an NBN Gateway registered user you can request access for missing datasets via the link 'Open interactive map in new window' below.

Distribution elsewhere: Widespread in continental Europe including Denmark, Finland, Norway, Sweden, the Mediterranean area (Spencer, 1976: 128), Germany (Spencer, 1976: 546), Canary Is., Czech Republic, Estonia, Italian mainland, Lithuania, Malta, Poland, Spanish mainland and Switzerland (Martinez in Fauna Europaea).

NBN interactive distribution map(s) of known host species in Great Britain and Ireland and elsewhere:

Parasiitoids:

Biodiversity Heritage Library
Bladmineerders van Europa
British leafminers
Encyclopedia of Life
Fauna Europaea [128908]
NBN Gateway