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GEUM. Avens. [Rosaceae] |
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Five species of Geum are recorded in Britain. These include the native Water Avens (G. rivale), Hybrid Avens (G. x intermedia) and Wood Avens (Geum urbanum). Only one Diptera miner, the agromyzid Agromyza idaeina, is recorded on Geum in Britain. Elsewhere the agromyzid Agromyza idaeina is recorded mining Geum. Six non-Diptera miners are recorded on Geum in Britain (see below). Elsewhere one additional British non-Diptera miner is recorded on Geum (see below). A key to the European miners, based on characteristics of the mines, immature stages and where relevant the larval cases, recorded on Geum is provided in Bladmineerders van Europa. This includes Agromyza idaeina, Coleophora potentillae, Incurvaria praelatella, Metallus lanceolatus, Stigmella aurella and Stigmella splendidissimella but not Cnephasia incertana, Coleophora ahenella; Stigmella geimontani or Stigmella pretiosa. |
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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# > Details of mine unknown
Pegomya rubivora (Coquillett, 1897) [Diptera: Anthomyiidae] 1a > Leaf-miner: Initially a linear mine which later develops into a conspicuous blotch; frass in two rows in linear section, scattered irregularly in the blotch. Larval mandibles with two teeth (Spencer, 1976). Corridor, gradually and considerably widening towards the end. Frass in two rows in the corridor part, further up dispersed irregularly. Pupation outside the mine (Bladmineerders van Europa). A short broad upper surface corridor leading to a long blotch between veins (British leafminers).
Agromyza idaeina (Kaltenbach, 1853) [Diptera: Agromyzidae]. 1b > Leaf-miner: A long linear mine, never widening into a blotch at end (Spencer, 1976: 107-8, fig. 167). Long upper-surface corridor. Many straight stretches, often along the midrib. Frass in discrete grains, here and there in thread fragments, but never in pearl strings. Pupation outside the mine (Bladmineerders van Europa). A long straight mine, which is sometimes branched. Found in the upper leaf surface (British leafminers).
Agromyza filipendulae Spencer, 1976 [Diptera: Agromyzidae]. 1c > Leaf-miner: Mine frequently starting along leaf margin, initially linear, later developing into an elongate blotch, frass in two distinct rows, even at end (Spencer, 1972: 30, fig. 74; Spencer, 1976: 144, fig. 263A). First a long corridor, its initial part often along the leaf margin or a thick vein. Rather suddenly the corridor widens into a broad blotch. The corridor contains much, amorphous frass that sometimes seems to fill the entire corridor (lower picture). In the blotch the frass is in black strings and coarse lumps. (In rainy weather they liquify and loose their shape). Pupation outside the mine (Bladmineerders van Europa). A narrow upper surface gallery to start, then broadening and zigzagging to create a false blotch (British leafminers).
Agromyza sulfuriceps Strobl, 1898 [Diptera: Agromyzidae]. 1d > Leaf-miner: Mine irregularly linear, even forming secondary blotch. Pupation in mine (Spencer, 1972: 93 (fig. 315). Very shallow, irregularly branched corridor, sometimes a narrow blotch. The mine is upper-surface, sometimes also interparenchymatous. The colour is pale green, larer more rust-coloured. Frass in small, widely spaced grains. Papation takes place within the mine. Hibernation in the mine, among fallen leaves (Bladmineerders van Europa).
Phytomyza heringiana Hendel, 1922 [Diptera: Agromyzidae]. |
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Key for the identification of British non-Diptera mines recorded on
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Note: The larvae of mining Coleoptera, Hymenoptera and Lepidoptera may live in a corridor mine, a corridor-blotch mine, a blotch mine, a case, a rolled or folded leaf, a tentiform mine or sandwiched between two more or less circular leaf sections in later instars. Larva may pupate in a silk cocoon. The larva may have at least six legs (although they may be reduced or absent), a head capsule and chewing mouthparts with opposable mandibles (see video of a gracillarid larva feeding). Larvae of Hymenoptera and Lepidoptera usually also have abdominal legs (see examples). Frass, if present, never in two rows. Unless feeding externally from within a case the larva usually vacates the mine by chewing an exit hole. Pupa with visible head appendages, wings and legs which lie in sheaths (see examples).
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1a > Miner and case bearer. The larva lives outside the mine, protected by a case, and feeds on the underlying plant tisses via a hole cut in the epidermis. Mine does not contain frass (Coleophora species) 1b > Miner, but not a case-bearer, although it may live sandwiched between two more or less circular sections cut from the leaf in later instars e.g. Incurvaria species. The larva lives mainly inside the mine. Mine usually contains frass |
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2a > Leaf-miner and case-bearer: The case resembles that of C. violacea, but does not lie so flat again the leaf as this species (having a mouth angle of 30 to 50°). C. violacea also has a case which bulges in the middle, whereas in C. potentillae the case tapers towards the posterior (British leafminers). Immediately after emergence the larva makes a full depth, quickly widening, corridor, with frass as small grains in a broad central band. Finally results a blotch of 2 x 5 mm, from which the youth case is cut. The fully developed case is a hairy, greyish brown to silver grey lobe case of about 1 cm long, with a clearly laterally compressed end; the mouth angle is about 90°. The case is difficult to separate from that of C. ochripennella (Bladmineerders van Europa).
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Coleophora potentillae (Elisha, 1885) [Lepidoptera: Coleophoridae].
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3a > 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 (Bladmineerders van Europa).
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Cnephasia incertana (Treitschke, 1835) [Lepidoptera: Tortricidae].
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3b > Leaf-miner: Small (less than 1 cm), full depth blotch, transparent when fresh, starting at the leaf margin, usually near the leaf tip; frass in scattered grains. The larva makes an elliptic double sided excision to form a case. Subsequently, it continues feeding within the case (Bladmineerders van Europa).
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Incurvaria praelatella (Denis and Schiffermüller, 1775) [Lepidoptera: Incurvariidae].
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3c > Leaf-miner: The mine begins with short, rather broad corridor, that often is overrun by the later, large, very transparent full depth blotch. The mine begins somewhere in the centre of the leaf. Frass in many loose grains (Bladmineerders van Europa).
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Metallus lanceolatus (C. G. Thomson, 1870) [Hymenoptera: Tenthredinidae].
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3d > Leaf-miner: A long gallery with dispersed frass (British leafminers). Oviposition may be at either side of the leaf, not necessarily close to a vein. The mine is a not very tortuous corridor, not widened in the end. Frass in a broad central line. The mine strongly overlaps with the one of S. splendidissimella (Bladmineerders van Europa).
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Stigmella aurella (Fabricius, 1775) [Lepidoptera: Nepticulidae].
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3e > Leaf-miner: The initial gallery has frass in an interupted black line (British leafminers). Egg usually at the upperside of the leaf. The mine is a long, strongly vein-determined corridor. In the first part the frass lies in a rather narrow, often interrupted central line; further on the frass line is broader and more diffuse. Frequently more than one mine in a leaf (Bladmineerders van Europa).
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Stigmella pretiosa (Heinemann, 1862) [Lepidoptera: Nepticulidae].
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3f > Leaf-miner: A long sinuous gallery with narrow frass-line (British leafminers). Oviposition generally at the leaf upper side, not especially close to a vein. From there a long and slender corridor starts, with frass usually in a narrow central line. The corridor often crosses itself, but rarely a thick vein (Bladmineerders van Europa).
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| Stigmella splendidissimella (Herrich-Schäffer, 1855) [Lepidoptera: Nepticulidae]. |
| Last updated 01-Feb-2012 Brian Pitkin |  |
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