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

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 > 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 horticola is recorded on 160 plant genera in 31 families of which 55 plant genera in 19 families, but not yet on Inula, in Britain. On Inula elsewhere.

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

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

1b > Leaf miner: An irregularly linear mine which can be both on the upper and lower leaf surface. Pupation takes place either at the end of the mine in an exit slit cut in the leaf or on the ground (Spencer, 1972b: 70 (fig. 226), 73; Spencer, 1976: 407 (fig. 712), 408).

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 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].

1a >Leaf-miner and case-bearer:

2

1b > Leaf miner

3

2a > Leaf-miner and case-bearer: The larva makes at least two cases and leaves the empty case by the cut out leaf section. The early cases are compressed with keels, dorsally and laterally. Later cases are more tubular and hairy (from the hairy leaves, used to make the case). Larva in a spathulate leaf case. It is 10-12 mm long, straght, brown, tubular, patently hairy (depending on the hostplant), bivalved. The mouth angle is rather variable, usually around 45°. An unusual character of this species is that after each moult the larva makes a new case; the old, vacated case is left at the place where the new one is made, at the leaf margin.

On Eupatorium, Inula and Pulicaria in Britain and elsewhere. Mainly distributed in southern England and Wales. A colony has also been located in York, so it may occur elsewhere. Widespread in continental Europe.

Coleophora conyzae Zeller, 1868 [Lepidoptera: Coleophoridae].

2b > Leaf-miner and case-bearer: Larva mines leaves. On Eupatorium the case is extended at the anal end by adding silk and widened by cutting a ventral gusset. On Inula the case is firstly extended by adding rings of leaf-cuticle at the oral end, before reverting to the method used when on Eupatorium. The full-grown case is 10 mm long. A slender tubular silken case, about 10 mm long, straw coloured, three valved. Mouth angle about 30°.

On Cirsium, Eupatorium, Inula and Pulicaria in Britain and Achillea, Anthemis, Carduus, Cirsium, Eupatorium, Inula, Leucanthemum, Pulicaria and Tanacetum elsewhere. Widespread in England. Also recorded in Republic of Ireland. Widespread in continental Europe.

Coleophora follicularis (Vallot, 1802) [Lepidoptera: Coleophoridae].