Key for the identification of the known mines of British
Diptera recorded on Lapsana

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).

See Key to non-Diptera.

1a > Stem-miner: External stem-miner (Spencer, 1972b: 61).

On Sonchus oleraceus, but not yet on Lapsana, 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].

1a > Stem miner: An external stem mine with frass in two rows of disconnected strips. Pupation in stem at end of mine (Spencer, 1972b: 25; Spencer, 1976: 61 (fig. 63B), 65-6)..

Polyphagous. On Campanula, Jasione, Phyteuma [Campanulaceae], Crepis, Hypochaeris and Lapsana [Asteraceae] in Britain and additional genera of both families elsewhere. Uncommon in Britain - recorded in London, Warwick and Cambridge. Uncommon but Widespread in continental Europe.

Ophiomyia heringi Stary, 1930 [Diptera: Agromyzidae].

1b > Leaf-miner

2

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

3

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

4

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.

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, including Lapsana, in Britain. 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 (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, 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].

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, 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) 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 Lapsana in Britain.

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

4b > Leaf-miner: A linear mine commencing with a conspicuous regular spiral and then continuing a considerable distance more or less straight (Spencer, 1976: 245).

Upper-surface corridor. The first part is wound in a dense spiral that quickly turns brown. The spiral continues in a long, generally unbranched corridor that maintains almost the same width. Frass in long thick strings. When the mine is positioned near the leaf margin the spiral part may be missing; the thick frass strings then are sufficiently characteristic. Pupation outside the mine; exit slit in lower epidermis.

Long upper surface gallery starting with a spiral of 6 to 8 turns (as shown). Frass in conspicuous narrow linear lines.

On Aster, Eupatorium, Helianthus, Lapsana and Solidago [Asteraceae] and Galeopsis [Lamiaceae] in Britain and continental Europe. Widespread in England. Also recorded in the Republic of Ireland. Widespread in continental Europe and recorded in Canada.

Liriomyza eupatorii (Kaltenbach, 1873) [Diptera: Agromyzidae].

4c > Leaf-miner: Larva mining both lower and upper surface, unusually long, linear, conspicuously broad, frequently largely on the underside of the leaf. Pupation external (Spencer, 1972b: 76 (fig. 251); Spencer, 1976: 445 (fig. 780), 446).

Corridor mine. The first part consists of a very long and narrow lower-surface corridor; the mine is quite shollow here, and often inconspicuous. The second part is upper-surface, uusally much shorter, and widens abruptly. Pupation outside the mine.

On Crepis, Hieracium, Lapsana, Picris, Pilosella, Senecio, Sonchus and Taraxacum 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, 1823 [Diptera: Agromyzidae].

4d > Leaf-miner: The mine begins with a very narrow full depth corridor, that ends upon the midrib. Subsequently a broad corridor, or rather an elongated blotch, is made overlying the midrib; from here broad, lobe-like extensions are made into the blade. Frass in discrete grains. Secondary feeding lines conspicuous. The larva is capable of leaving the mine and restarting in a new leaf, in which case the association with the midrib may be lost. Pupation after vacation of the mine.

On Cichorium, Crepis, Hieracium and Taraxacum, but not yet on Lapsana, in Britain and additionally other genera of Asteraceae elsewhere. North-east Scotland, also throughout Ireland and continental Europe, except the Mediterranean area.

Trypeta immaculata (Macquart, 1835) [Diptera: Tephritidae].