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 > Primary blotch mine tending to fill a lobe of the palmate leaf. Near the beginning of the mine, the frass is concentrated in roughly concentric rings to form a dark spot and elsewhere the frass is arranged in loose series of lines and arcs. Mines often appear rusty and mottled. Larva leaves the mine through the lower surface to pupate externally, presumably in the soil.

On Trollius europaeus in Britain and continental Europe. Recorded in Britain from a single male caught in a yellow water trap at Malham Tarn, North York and ten empty mines on Trollius europaeus in Inverewe Gardens, near Gairloch in the Highlands. Widespread in continental Europe.

Phytomyza trolliivora Hering, 1935 [Diptera: Agromyzidae].

1b > Linear mine, possibly forming a secondary blotch.

2

2a > Simple white linear mine; frass deposited in scattered black spots. Pupation external. Puparium black

On Trollius europaeus in Britain and continental Europe. Recorded in Britain from a single male caught in a yellow water trap at Malham Tarn, North York. Widespread in continental Europe.

Phytomyza trollii Hering, 1930 [Diptera: Agromyzidae].

2b > Closely winding linear mine; the adjoining sections usually forming a secondary pseudo-blotch; frass variably coloured and in diffuse patches. Pupation internal in a 'pupal cradle'.

On Trollius europaeus in Britain and continental Europe. Known only from Perth in Britain and Germany in continental Europe.

Phytomyza trolliophila Hering, 1949 [Diptera: Agromyzidae].