Note: Diptera larvae may live in a corridor mine, a corridor-blotch mine, or a blotch mine, but never in a case, a rolled or folded leaf, a tentiform mine or sandwiched between two more or less circular leaf sections in later instars. Pupation never in a cocoon. All mining Diptera larvae 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. The larvae lie on their sides within the mine and use their pick-like mouthparts to feed on plant tissue. In some corridor miners frass may lie in two rows on alternate sides of the mine. In order to vacate the mine the fully grown larva cuts an exit slit, which is usually semi-circular (see Liriomyza huidobrensis video). The pupa is 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).

1a > External stem-miner

On Sonchus oleraceus, but not yet on Cicerbita in Britain. On Crepis, Lapsana and Sonchus elsewhere. Uncommon, but locally abundant in Britain including London, Essex and Hunts. Widespread in continental Europe. Also recorded in Brazil, Canada, and the Afro-tropical, Australian, East Palaearctic and Oriental regions.

Phytoliriomyza arctica (Lundbeck, 1901) [Diptera: Agromyzidae].

1b > Leaf-miner

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2a > Leaf-miner: Mine primarily associated with the mid-rib.

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2b > Leaf-miner: Mine not primarily associated with the mid-rib.

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3a > 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 (Bladmineerders van Europa). A linear mine on the upper surface, usually following the midrib and showing side branches along the veins. The frass is in strings (British leafminers).

On more than 40 host genera in 15 families in Britain including Sonchus and Cicerbita. Widespread throughout Britain. Also recorded in the Republic of Ireland. Widespread in continental Europe.

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

3b > Leaf-miner: A whitish blotch-mine along mid-rib, with offshoots into leaf blade. Pupation takes place at the base of the mid-rib. Puparium yellowish white

Mine of Ophiomyia cunctata on Taraxacum officinale Image: Willem Ellis (Bladmineerders van Europa)

On Crepis, Hypochaeris, Lapsana, Mycelis, Picris, Sonchus, Taraxacum and possibly Bellis, but not yet on Cicerbita in Britain and additional genera of Asteraceae elsewhere. Widespread in Britain and throughout much of Europe.

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

3c > Leaf-miner: A whitish blotch-mine along the mid-rib, with lateral offshoots into the leaf blade. Pupation internal. Puparium pale, whitish-yellow

Mine of Ophiomyia pulicaria on Taraxacum officinale. Image: Willem Ellis (Bladmineerders van Europa)

On Crepis, Hieracium, Hypochaeris, Leontodon, Picris, Pilosella, Sonchus and Taraxacum, but not yet on Cicerbitain Britain and additional genera of Asteraceae elsewhere. Widespread and common in Britain and continental Europe. Range extending east to Siberia. Also recorded from Canada.

Ophiomyia pulicaria (Meigen, 1830) [Diptera: Agromyzidae].

3d > Leaf-miner: A white mine along mid-rib, with offshoots into leaf blade. Pupation internal at base of mid-rib. Puparium whitish

On Cicerbita, 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].

4a > 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 (Bladmineerders van Europa). A long whitish upper surface corridor, which eventually goes lower surface (British leafminers).

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 are polyphagous and widespread in Britain and elsewhere, although syngenesiae is almost entirely restricted to Asteraceae (see also 'atricornis').

Chromatomyia horticola is recorded on 55 plant genera in 19 families in Britain but not yet on Cicerbita or Sonchus in Britain.

Chromatomya syngenesiae is recorded in Britain on 27 plant genera in the family Asteraceae, including Sonchus, and many more genera elsewhere, but not yet on Cicerbita in Britain.

Chromatomyia 'atricornis' has been recorded on Cicerbita and Sonchus in Britain.

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

4b > Leaf-miner: Larva mining both lower and upper surface, unusually long, linear, conspicuously broad, frequently largely on the underside of the leaf. Pupation external. Puparium black

On Crepis, Hieracium, Lapsana, Picris, Pilosella, Senecio, Sonchus and Taraxacum, but not yet on Cicerbita, in Britain and additionally other genera of Asteraceae elsewhere. Widespread in southern Britain, also Sutherland, Inner Hebrides and Warwick. Also recorded in the Republic of Ireland and Widespread in much of Europe.

Phytomyza marginella Fallén, 1923 [Diptera: Agromyzidae].

4c > Leaf-miner: A small primary blotch, often several larvae feeding together.

On Sonchus arvensis, Sonchus asper, Sonchus oleraceus and Sonchus palustris, but not yet on Cicerbita, in Britain. On Cichorium, Lactuca, Mycelis, Prenanthes and Sonchus elsewhere. Widespread, at least in south, in Britain. Widespread and common in much of Europe. Also recorded in Canada.

Liriomyza sonchi Hendel, 1931 [Diptera: Agromyzidae].