Trigonella [Fabaceae] in Leaf and stem mines of British flies and other insects

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

TRIGONELLA. Fenugreeks. [Fabaceae]

Twenty-one species of Trigonella are recorded in Britain. All are introduced and include Blue Fenugreek (T. caerulea), Sickle-fruited Fenugreek (T. corniculata), Fenugreek (T. foenum-graecum), Egyptian Fenugreek (T. hamosa) and Star-fruited Fenugreek (T. monspeliaca).

Seven British miners are recorded on Trigonella.

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 Trigonella is provided in Bladmineerders van Europa.

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

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: Larva producing a short narrow linear mine not associated with the margin, which then develops into a conspicuous white blotch centred on the mid-rib. At the end of feeding the larva lies for one or two days along the mid-rib. Pupation external (Spencer, 1972b: 37 (fig. 114b); Spencer, 1976: 126, fig. 213A).

Broad and short hook-like upper-surface corridor, ending in a little blotch in the centre of a leaflet. The blotch is upper-surface as well, but has some deep spots, giving the mine a mottled appearance when hold against the light. Frass in the blotch in a few large lumps. Pupation outside the mine.

A short, broad gallery leading to a conspicuous, roundish white blotch in the centre of the leaf. The blotch is upper surface with full depth spots - comprising of large clumps of frass.

Puparium reddish

On Medicago, Melilotus and Trifolium, but not yet on Trigonella, in Britain and in addition other genera of Fabaceae elsewhere. Common and widely distributed in England. Also recorded in the Republic of Ireland. Widespread and common throughout Europe.

Agromyza nana Meigen, 1830 [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, in a, usually lower-surface, pupal 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 Trigonella, in Britain.

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

1c > Leaf-miner: Corridor leaf-mine in leaves. An upper surface linear mine with frass in conspicuous greenish strips, largely alternating at each side of the channel (Spencer, 1976: 241).

Upper-surface, unbranched corridor, relatively broad from the start on, but only weakly widening subsequently. The fresh mine is bright green, but turns whitish, later brown, quickly. Frass in a wide green band in the centre of the corridor, with small black granules at either side. Pupation outside the mine.

Forms an upper surface mine, with the frass in a green strips.

Liriomyza congesta puparium
Image: © Willem Ellis (Bladmineerders van Europa)

Polyphagous. On numerous genera of Fabaceae, but not yet on Trigonella, in Britain. Widespread in Britain. Also recorded in the Republic of Ireland and widespread and common throughout most of Europe

Liriomyza congesta (Becker, 1903) [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.

Liriomyza strigata larva, lateral Image: © Willem Ellis (Bladmineerders van Europa)
Polyphagous. On more than 40 host genera in 15 families, but not yet on Trigonella, in Britain and elsewhere. Widespread throughout Britain. Also recorded in the Republic of Ireland. Widespread in continental Europe.
*Liriomyza strigata* (Meigen, 1830) [Diptera: Agromyzidae].
1e > 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 Trigonella, 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].

Key for the identification of the known mines of British
non-Diptera recorded on Trigonella

1a > Leaf-miner: The first generation initially forms an unmistakable leaf-mine on Anthyllis vulneraria, but the second generation feeds on the flowers. Feeding signs on other plants vary in appearance. Larvae can move between sewn leaves, and more than one larva may be found together. Larvae in a small full depth blotch, often with extensions. Frass concentrated in one corner of the mine. The mining activities may cause the leaf to roll inwards. Older larvae live free among spun leaves, but still they may make then full depth mines by feeding on the leaf tissue from a small opening.

On Anthyllis, Medicago, Onobrychis, Ononis and Trifolium, but not yet on Trigonella, in Britain and Anthyllis, Chamaecytisus, Coronilla, Cysisus, Dorycnium, Galega, Glycine, Hymenocarpos, Lathyrus, Lotus, Medicago, Melilotus, Onobrychis, Ononis, Ornithopus, Oxytropis, Phaseolus, Psoralea, Trifolium, Trigonella and Vicia elsewhere. Britain including the Channel Is. and Northern Ireland. Also recorded in the Republic of Ireland. Widespread in continental Europe.

Aproaerema anthyllidella (Hübner, 1813) [Lepidoptera: Gelechiidae].

1b > Leaf-miner: In the first instar the larva mines the leaves, forming short, irregular, blotch-like mines, but in later instars it lives externally, feeding in spun leaves and often twisting those of tender shoots. Larval head light-brown or yellowish brown, edged with black postero-laterally, ocellar area blackish; prothoracic plate black edged with whitish anteriorly; abdomen dull dark green; pinacula distinct, black, sometimes brownish but with black bases to setae; anal plate large, black (Bradley et al., 1973). Small, full depth mine without a definite shape; little frass. Some silk is deposited in the mine. The larva soon leaves the mine and continues feeding among spun leaves.

Polyphagous. On numerous genera and species of several plant families, but not yet on Trigonella, in Britain. On numerous genera and species of several plant families, including Trigonella, elsewhere. Widespread in Britain and continental Europe. Also recorded from the Channel Is.

Cnephasia incertana (Treitschke, 1835) [Lepidoptera: Tortricidae].


	Last updated 04-Feb-2018 Brian Pitkin