Key for the identification of the known mines of British
insects (Diptera and non-Diptera) recorded on Arnoseris

1a > Leaf-miner: Mine linear, whitish, both upper and lower surface. Pupation internal, at the end of the mine with the anterior spiracles projecting through the epidermis (Spencer, 1976: 433).

Upper-surface, less often lower-surface corridor. Frass in isolated grains. Pupation within the mine, usually in a lower-surface puparial chamber.

A long whitish upper surface corridor, which eventually goes lower surface.

Two highly polyphagous species of Chromatomyia, with indistinguishable mines, have been recorded in Britain. These are syngenesiae (Hardy) and horticola (Goureau, 1851) which can only be distinguished by the male genitalia. Both species are widespread in Britain and elsewhere, although syngenesiae is almost entirely restricted to Asteraceae. Records on Asteraceae not based on examination of male genitalia are treated in this account as Chromatomyia 'atricornis'.

Chromatomya syngenesiae is recorded in Britain on 27 plant genera in the family Asteraceae, including Arnoseris, and many more genera elsewhere.

Chromatomyia 'atricornis' is recorded on Arnoseris elsewhere.

Chromatomyia horticola (Goureau, 1851) [Diptera: Agromyzidae]
OR
Chromatomyia syngenesiae Hardy, 1849 [Diptera: Agromyzidae].

1b > Leaf-miner: A small somewhat irregular, elongate blotch.

On Leontodon and Taraxacum, but not yet on Arnoseris, in Britain and Aposeris, Arnoseris, Leontodon and Taraxacum elsewhere, Widespread in Britain and continental Europe.

Liriomyza taraxaci Hering, 1927 [Diptera: Agromyzidae].