The leaf and stem mines of British flies and other insects

(Coleoptera, Diptera, Hymenoptera and Lepidoptera)

by Brian Pitkin, Willem Ellis, Colin Plant and Rob Edmunds


GNAPHALIUM. Cudweeds. [Asteraceae]

Eleven species of Gnaphalium are recorded in Britain. These include the native Jersey Cudweed (G. luteoalbum), Marsh Cudweed (G. uliginosum), Highland Cudweed (G. norvegicum), Dwarf Cudweed (G. supinum) and Heath Cudweed (G. sylvaticum). Jersey Cudweed (G. luteoalbum) is protected under Schedule 8 of the Wildlife and Countryside Act, 1981.

Four British miners recorded on Gnaphalium.

The polyphagous agromyzid Liriomyza trifolii has been recorded in quarantine in Britain (Pitkin & Plant in British leafminers). See also Liriomyza species in Glasshouses and/or Quarantine Interceptions.

A key to the European miners recorded on Gnaphalium is provided in Bladmineerders van Europa.

Marsh Cudweed - Gnaphalium uliginosum. Image: © Linda Pitkin
Marsh Cudweed
Gnaphalium uliginosum

Key for the identification of the known mines of British
insects (Diptera and non-Diptera) recorded on Gnaphalium

1a > Leaf and Stem-miner: An external stem mine on Gnaphalium sylvaticum (Spencer, 1972b: 27). In the latter a single larva moves from leaf to leaf, each leaf with 2-4 broad diverging tracks extending rarely more than two-thirds of the length of the leaf from the petiole into the leaf lamina; frass concentrated in the petiolar part of the mine. Pupation in mine (Spencer, 1972b: 27).

Mine in the leaf base of the lower leaves, often close to the midrib. From the leaf base corridors radiate into the leaf disk. Primary feeding lines in fresh mines well visible. Frass sparingly, granular. Puaparium in the mine, in the leaf base.

On Antennaria and Gnaphalium in Britain. Uncommon in Britain (Hereford and Perth). Also recorded from Germany and Lithuania.

Ophiomyia gnaphalii Hering, 1949 [Diptera: Agromyzidae].

1b > 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 Gnaphalium, in Britain.

Chromatomyia horticola (Goureau, 1851) [Diptera: Agromyzidae]

1d > 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, but not yet on Gnaphalium, in Britain,. Widespread throughout Britain. Also recorded in the Republic of Ireland. Widespread in continental Europe.

Liriomyza strigata (Meigen, 1830) [Diptera: Agromyzidae].

1e > Leaf-miner: Rather narrow corridor, untidy and sometimes branched, starting from the base of the leaf, in particular the midrib. Sides of the corridor irregularly eaten out, not really parallel. Frass mostly present, and then in a central line. The larva is capable of leaving the mine and start a new one elsewhere. These later mines are much broader, and the frass is scattered irregularly..

Mine of Orthochaetes insignis on Prunella vulgaris
Mine of Orthochaetes insignis on Prunella vulgaris
Image: © Jean-Yves Baugnée (Bladmineerders van Europa)

Host plants unknown in Britain. On numerous genera and species in several plant families, including Carduus, elsewhere. Recorded in southern England. Widespread in continental Europe.

Orthochaetes insignis (Aube, 1863) [Coleoptera: Curculionidae].

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