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

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 and many more genera elsewhere, but not yet on Conyza, in Britain.

Chromatomyia syngenesiae Hardy, 1849 [Diptera: Agromyzidae].

1b > Leaf miner:

A short linear mine in first instar, later producing a circular or oval blotch. Frass is excreted in a black mass prior to pupation; puparium firmly glued with frass within the mine (Spencer, 1976: 306).

Large, whitish, upper-surface blotch, preceded by a short corridor that often is overrun later by the developing blotch. The larva hardly produces any frass; the few grains that are present are black and rather coarse. But when the larva is about to pupate, it empties its intestine, which has the effect that the puparium is anchored in the mine by dried frass.

The initial gallery by the first instar larva then leads to a whitish blotch. The puparium is fixed to the inside of the mine by an accumulation of frass.

On Aster, Bellis and Erigeron, but not yet on Conyza, in Britain and additional genera of Asteraceae elsewhere. Widespread in southern England and continental Europe. Also recorded in Canada, Argentina, South Africa, India, Australia and Papua New Guinea.

Calycomyza humeralis (von Roser) [Diptera: Agromyzidae].

1c > Leaf-miner: A distinctive mine primarily above mid-rib, with irregular short lateral offshoots into leaf blade. Pupation external (Spencer, 1972: 51 (fig. 172), 55; Spencer, 1976: 270, 271 (fig. 486)).

Branched, whitish, upper-surface corridor; main axis overlying the midrib; side branches overlying the main lateral veins. (In Campanula and Phyteuma the mine is much less branched, sometimes nothing more than a corridor on top of the midrib). Frass in rather long strings. Usually the mines begins as a long and narrow, shallow, tortuous lower-surface corridor that ends upon the midrib but otherwise is not associated with the leaf venation. Often this initial corridor is filled with callus, and then even less conspicuous. Pupation outside the mine.

A linear mine on the upper surface, usually following the midrib and showing side branches along the veins. The frass is in strings.

Polyphagous. On more than 40 host genera in 15 families, but not yet on Conyza, in Britain and elsewhere. Widespread throughout Britain. Also recorded in the Republic of Ireland. Widespread in continental Europe.

Liriomyza strigata (Meigen, 1830) [Diptera: Agromyzidae].

Upper surface corridor, often following the midrib for some distance. Frequently the very first part of the mine is lower-surface, and sometimes the entire mine remains at the lower surface. The corridor is wide from the start, with irregular sides. Frass initially in two rows of fine grains; further on the grains become larger and more irregular, sometimes forming pearl chains, and are dispersed less regularly. Pupation takes place either outside or within the mine. When the larva has left the mine a semicircular exit slit is made. When the puparium is formed within the mine the spiracles do not penetrate the epidermis, and an irregular semicircular opening is made in the epidermis in front of the puparium.

Mines down the leaf from the tip, then doubles back and then mines towards the apex, often doubling back a second time, towards the leaf base.

On Inula and Pulicaria, but not yet on Conyza, in Britain and additional genera of Asteraceae elsewhere. Widespread in Britain. Also recorded in the Republic of Ireland. Widespread in continental Europe and particularly common in the Mediterranean area

Phytomyza conyzae Hendel, 1920 [Diptera: Agromyzidae].

1e > Leaf-miner: A narrow upper surface linear branching mine without apparent feeding lines. Frass in isolated grains and pearl chains. At least in Erigeron older mines turn reddish-brown. Pupation external (Spencer, 1976: 413).

On Erigeron acer and Erigeron canadensis, but not yet on Conyza, in Britain and additional genera of Asteraceae elsewhere. Known only from Warwick in Britain. Widespread in continental Europe.

Phytomyza erigerophila Hering, 1927 [Diptera: Agromyzidae].