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

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: A narrow linear leaf-mine, which developes into a large blotch. Several larvae frequently feed together and the resulting mine can entirely fill the leaf (Spencer, 1976: 89).

The mine begins with a narrow, parallel sided corridor af 1-8 cm in length, with a nice double frass line. After the first moult the corridor is succeeded, and mostly overrun, by a large, primary, brown blotch. Frass in the initial corridor in short thread fragments, in the blotch in angular granules and thread fragments that often are branching (the frass is unusally sticky). Primary and secondary feeding lines conspicuous. The final mine often is very large and generally contains several larvae, because normally several mines develop on a leaf, and coalesce into one big blotch. Before pupation the larvae leave the mine through a semicircular exit slit that mostly, but not invariably, is in the upper epidermis.

The initial narrow gallery contains frass in a double line. It then expands to form a blotch mine. Several larvae may occupy a leaf to form a large blotch.

On numerous genera of Boraginaceae, including Anchusa, Borago, Cynoglossum, Echium and Pulmonaria in Britain and elsewhere. Widespread in Britain. Also recorded in the Republic of Ireland. Common and widespread throughout most of Europe.

Agromyza abiens Zetterstedt, 1848 [Diptera: Agromyzidae].

1b > Leaf-miner: Mine initially linear, later developing into a whitish blotch, becoming blackish. Pupation in mine on lower surface.

The mine begins as an upper surface blotch in the centre of the leaf, from where corridors radiate, each with one larva. After a while these rays fuse, resulting in one large, brown, blotch. Frass in irregular strings. Pupation in principle outside the mine, exit slit in lower epidermis (always?). Often the puparium protrudes from the opening.

On Symphytum, but not yet on Echium, in Britain. On Brunnera, Echium, Lithospermum and Symphytum elsewhere. Widespread in Britain and continental Europe.

Phytomyza medicaginis Hering, 1925 [Diptera: Agromyzidae].

1a > Leaf-miner: Mine upper-surface or, more often, lower-surface. At first a long, narrow, winding epidermal gallery with central, more or less deliquescent, reddish brown frass. The gallery abruptly widens into an elongate blotch that is epidermal at first but soon deeper; the blotch is brown with strikingly white margins. Epidermis finely wrinkled. Lower surface mines strongly contract the leaf (and often there is a mine at either side of the midrib). 2-3 Larvae in a blotch, each with its own initial corridor. Frass in large black grains in a central depot; moreover in the form of very thin threads stuck in a reticulate pattern in the epidermis.

Hosts in Britain unknown. On Anchusa, Cynoglossum, Echium, Myosotis and Symphytum elsewhere. First recorded in the UK in Kent (2004), when a moth was trapped.

Dialectica scalariella (Zeller, 1850) [Lepidoptera: Gracillariidae].