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

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, in a, usually lower-surface, pupal 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) 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'.

Chromatomyia 'atricornis' has been recorded on Helminthotheca in Britain.

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

1b > Leaf-miner: A whitish blotch mine along mid-rib, with offshoots into leaf blade. Pupation takes place at the base of the mid-rib (Spencer, 1972b: 25; Spencer. 1976: 63 (fig. 66)).

The mine begins as a very narrow, upper- or lower-surface corridor, somewhere in the blade. When this hits a thick vein the larva uses this to descend towards the midrib. From that moment the lave lives in the hollow midrib. From here short, lobate corridors enter the leaf blade. The larva may move to another leaf by way of the leaf base. The corridors in the leaf are virtually free of frass (at most a few grains where they leave the midrib); frass is concentrated in the base of the midrib. Here also the pupation takes place.

On Crepis, Helminthotheca, Hypochaeris, Lapsana, Mycelis, Picris, Sonchus, Taraxacum and possibly Bellis in Britain and additional genera of Asteraceae elsewhere. Widespread in Britain and throughout much of Europe.

Ophiomyia cunctata (Hendel, 1920) [Diptera: Agromyzidae].

1c > Leaf-miner: A white mine along mid-rib, with offshoots into leaf blade. Pupation internal at base of mid-rib.

In Asteraceae the larva mostly lives as a borer in the midrib of the leaves. From there short corridors are made into the blade. Also a corridor can be made overlying the midrib. In Euphorbia a small mine is made in the bracts of the inflorescence. The final mine strongly resembles the one of Liriomyza strigata, but the branches are vritually free from frass; this is acccumulated in the resting place of the larva, in the base of the midrib. There also pupation takes place.

Forms a mine along the midrib and has feeding spurs into the leaf. Pupation is in the mine at the base of the midrib.

On Cicerbita, Helmnthotheca, Leontodon, Sonchus and Taraxacum, in Britain and numerous other genera of Asteraceae elsewhere. Widespread in south, but not common, in Britain. Widespread in continental Europe.

Ophiomyia beckeri (Hendel, 1923) [Diptera: Agromyzidae].