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).

1 > Leaf-miner: There may be several mines to a leaf, which are initially blackish, short and linear. A blotch is later formed. Pupation external, normally on lower surface. Puparium greyish-brown

On Helleborus foetida in Britain and this and other Helleborus species elsewhere. Southern Counties and East Anglia in Britain. Widespread in continental Europe.

Phytomyza hellebori Kaltenbach, 1872 [Diptera: Agromyzidae].