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

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 > Stem or root miner

2

1b > Leaf miner

3

2a > Stem miner: An external stem mine. Pupation in the stem, near or even below ground level, with the anterior spiracles projecting through the epidermis (Spencer, 1976: 72-3).

On Lathyrus, Pisum and Vicia in Britain and Lathyrus and Pisum elsewhere. Widespread in the south of Britain. Widespread in much of Europe.

Ophiomyia orbiculata (Hendel, 1931) [Diptera: Agromyzidae].

2b > Stem miner: A long white mine mainly in the winged stem, frequently starting in leaf (Spencer, 1972b: 42).

The mine begins as a narrow under-surface corridor. It usually quickly becomes upper-surface, and also the following blotch part of the mine is upper-surface. Here and there in the blotch the larvae also eats from the palisade parenchyma, giving the mine a mottled aspect when held against the light, but less strongly than in A. lathyri. Frass in the initial corridor, if at all visible, in short threads; very little frass in the blotch. Pupation outside the mine.

The mine is in the wing of the stem, but often starts in leaf (though not always).

On Lathyrus latifolius and Lathyrus sylvestris in Britain and elsewhere. Widespread in Britain and continental Europe.

Agromyza varicornis Strobl, 1898 [Diptera: Agromyzidae].

3b > Leaf miner: An initially lower-surface linear leaf-mine, which later develops into large whitish blotch and appears pale and mottled from above, due to the variable depth of larval feeding. Less frequently feeding in upper surface or stem (Spencer, 1972b: 37, fig. 112); Spencer, 1976: 118).

The mine starts as a superficial lower-surface corridor. After its first moult the larva starts making a blotch, often close to the base of the leaflet. The blotch in principle is lower-surface, but may be interparenchymatous for some part. Moreover, in places the larva feeds from the palissade parenchyma. Seen from above the leaf appears mottled. The overall result is that the mine, despite its considerable size, is hard to find. The easiest way is to hold the leaves against the light: the large larvae than are conspicuous. Frass in coarse grains, both in the corridor and in the blotch; in the corridor they are widely spaced. Pupation outside the mine.

Puparium reddish

On Lathyrus grandiflorus, Lathyrus latifolius, Lathyrus rotundifolius, Lathyrus tuberosus and Pisum sativum in Britain and additional species and genera of Fabaceae elsewhere. Widespread in southern England - Kent, Surrey, Warwick and Cambridge and Widespread in continental Europe.

Agromyza lathyri Hendel, 1923 [Diptera: Agromyzidae].

3c > 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, including Lathyrus, in Britain.

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

3d > Leaf miner: An upper surface linear mine with frass in conspicuous greenish strips, largely alternating at each side of the channel. Puparium yellow

Polyphagous. On numerous genera of Fabaceae, including Lathyrus, in Britain and elsewhere. Widespread in Britain. Also recorded in the Republic of Ireland and widespread and common throughout most of Europe.

Liriomyza congesta (Becker, 1903) [Diptera: Agromyzidae].

3e > Leaf miner: A long linear mine, normally starting on lower surface, frass in black strips alternately at sides of mine (Spencer, 1972b: 58).

Long whitish corridor, almost always lower-surface at first, then becoming largely or totally upper-surface. Because lower- and upper-surface tracts often cross the leaf looks distinctly mottled whe held against the light. The final part of the corridor is generally upper-surface. The corridor often follows a thick vein for a considerable distance. Frass in alternating thread fragments. Pupation outside the mine.

On Lathryus, Pisum and Vicia in Britain and Lathryus and Pisum elsewhere. Only known from Kent, Surrey, Herts and Warwick in Britain. Widespread in continental Europe.

Liriomyza pisivora Hering, 1957 [Diptera: Agromyzidae].

3f > Leaf-miner: A short, irregular, linear upper surface mine on any part of the leaf. Also recorded from young pods (Bland, 1997a).

Long corridor mine. As a rule the first part of the mine is lower-surface, the later part upper-surface. Often the loops are so dense that a secondary blotch is the result. Because upper- and lower-surface corridor segments often cross, the mine obtains a strange array of transparant patches. There is no association with the midrib. Frass in strings and thread fragments. Pupation outside the mine; exit slit in upper epidermis.

Mine not associated with the veins or midrib of the leaf (It is this character which enables distinction from another Agromyzid pest species - Liriomyza huidobriensis). The larvae may leave one leaf (if not large enough) and enter another leaf, via the petiole). It exits the leaf to pupate through a semi-circular slit in the upper surface of the leaf.

Polyphagous. On 119 plant genera in 31 plant families of which only 4 plant genera in 2 plant families, but not yet on Lathyrus, in Britain. Local, probably introduced to Britain. Widespread in continental Europe particularly in Botanical Gardens and glasshouses. Also recorded in Egypt.

Liriomyza bryoniae (Kaltenbach, 1858) [Diptera: Agromyzidae].

3g > Leaf-miner: A narrow linear mine adjoining the leaf margin in the first instar, which later develops into an irregular blotch with conspicuous lumps of greenish frass (Spencer, 1976: 302).

The first instar larva makes a narrow upper-surface corridor along the leaf margin. After it has moulted it begins a large upper-surface blotch. Frass in conspicuous green lumps, that can run out irregularly. Pupation outside the mine.

Forms a narrow linear mine by the margin of the leaf which later develops into a blotch. The blotch has clumps of greenish frass.

On Astragalus and Colutea, but not yet on Lathyrus, in Britain and Anthyllis, Astragalus, Cicer, Colutea, Coronilla, Cytisus, Lathyrus, Oxytropis, Securinega and Vicia elsewhere. Widespread in continental Europe.

Phytoliriomyza variegata (Meigen, 1830) [Diptera: Agromyzidae].