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CENTAUREA. Knapweeds, Star-thistles and Cornflowers. [Asteraceae] |
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Forty species of Centaurea are recorded in Britain. These include the native Common Knapweed (C. nigra), Greater Knapweed (C. scabiosa) and Slender Knapweed (C. debeauxii) and introduced Knapweeds, Star-thistles and Cornflowers. Seven Diptera miners, the agromyzids Chromatomyia 'atricornis', Liriomyza centaureae, Liriomyza strigata, Phytomyza autumnalis, Phytomyza cinerea, Phytomyza continua and Phytomyza spinaciae are recorded on Centaurea in Britain, but the record of Phytomyza continua requires confirmation. The agromyzids Melanagromyza oligophaga and Napomyza hirticornis are recorded boring stems of Centaurea in Britain. The tephritid Philophylla caesio is tentatively recorded on Centaurea in Britain. It is recorded as a petiole miner on Urtica elsewhere. Elsewhere the agromyzids Aulagromyza similis, Chromatomyia horticola, Chromatomyia syngenesiae, Liriomyza bryoniae, Liriomyza centaureae, Liriomyza strigata, Liriomyza trifolii, Ophiomyia beckeri, Ophiomyia curvipalpis, Phytomyza autumnalis, Phytomyza cinerea, Phytomyza spinaciae and Phytomyza spoliata and the tephritid Philophylla caesio are recorded mining Centaurea. |
 Common Knapweed Centaurea nigra |
| Elsewhere the agromyzids Napomyza lateralis and Melanagromyza dettmeri are recorded in stems of Centaurea. Five non-Diptera leaf- miners are recorded on Centaurea in Britain (see below). Elsewhere eight British non-Diptera miners are recorded on Centaurea (see below). A key to the European miners, based on characteristics of the mines, immature stages and where relevant the larval cases, recorded on Centaurea is provided in Bladmineerders van Europa. This includes Aulagromyza similis, Botanophila centaureae, Chromatomyia cf. syngenesiae, Liriomyza centaureae, Liriomyza strigata, Ophiomyia beckeri, Ophiomyia curvipalpis, Phytomyza autumnalis, Phytomyza cinerea, Phytomyza montana, Phytomyza spinaciae, Phytomyza spoliata, Agonopterix arenella, Agonopterix carduella, Agonopterix propinquella, Agonopterix subpropinquella, Apterona helicoidella, Cnephasia asseclana, Cnephasia lineata, Cnephasia sedana, Cnephasia stephensiana, Coleophora brevipalpella, Coleophora caelebipennella, Coleophora conspicuella, Coleophora didymella, Coleophora paripennella, Coleophora peribenanderdi, Coleophora rectilineella, Comasinus setiger, Jordanita chloros, Jordanita globulariae, Jordanita graeca, Jordanita notata, Orthochaetes setiger, Pseudorchestes pratensis, Pseudorchestes cinereus and Pseudorchestes heringi, Pseudorchestes ermischi, Pseudorchestes persimilis, Scrobipalpa acuminatella, Scrobipalpa halonella, Scrobipalpa pauperella , Scrobipalpa perinii, Sphaeroderma testaceum, Sphaeroderma rubidum but not Liriomyza bessarabica or Scrobipalpula psilella. |
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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). 1a > Leaf-miner: Mine primarily associated with mid-rib. 1b > Leaf-miner: Mine not primarily associated with mid-rib. 2a > 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 (Bladmineerders van Europa). A linear mine on the upper surface, usually following the midrib and showing side branches along the veins. The frass is in strings (British leafminers).
Liriomyza strigata (Meigen, 1830) [Diptera: Agromyzidae]. 2b > Leaf-miner: Larva feeds along the mid-rib, predominantly on the lower surface and there is little evidence of gall-like swelling. Pupation takes place at the base of the midrib. Puparium whitish. Record on Centaurea requires confirmation.
Phytomyza continua Hendel, 1920 [Diptera: Agromyzidae]. 3a > Leaf-miner: Several larvae feed together. Mine a brownish blotch, at apex of leaf segment,, Pupation in mine. Puparium brown
Phytomyza cinerea Hendel, 1920 [Diptera: Agromyzidae]. 3b > Leaf-miner: Larvae feed singly. 4a > Leaf-miner: Long narrow interparenchymal mine, greenish. Pupation in leaf at end of mine. Puparium white
Phytomyza spinaciae Hendel, 1928 [Diptera: Agromyzidae]. 4b > Leaf-miner: Mine not interparenchymal. 5a > 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 (Bladmineerders van Europa). A long whitish upper surface corridor, which eventually goes lower surface (British leafminers).
Chromatomyia
horticola (Goureau, 1851) [Diptera: Agromyzidae]. 5b > Leaf-miner: A short irregular linear mine with frass in more or less connected threads.
Liriomyza centaureae Hering, 1927 [Diptera: Agromyzidae]. 5c > Leaf-miner: Mine long, distinctly greenish. Pupation in mine. Puparium white in early generations and black and shiny in autumn
Phytomyza autumnalis Griffiths, 1959 [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: A relatively large (12-15 mm), dark brown, lightly curved two-valved sheath case with a narrow ventral keel. Mouth angle 30-45 (Bladmineerders van Europa).
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Coleophora conspicuella Zeller, 1849 [Lepidoptera: Coleophoridae].
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2b > Leaf-miner and case-bearer: Larva mines leaves (British leafminers). The larva builds a case from silk, resembling a razor shell in appearance. (UKMoths). The full-grown case is 12 mm long and blackish-brown (British leafminers). The full grown larva lives in a blackish brown trivalved tubular silken case of about 8 mm. The mouth angle is 0°-10°, causing the case to lay almost flat on the leaf (Bladmineerders van Europa).
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Coleophora paripennella Zeller, 1839 [Lepidoptera: Coleophoridae].
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2c > Leaf-miner and case-bearer: The larva forms a case, approximately 11-12 mm long, beneath a thistle leaf, although burdock may sometimes be used. The shape of the ochreous case varies as, when being enlarged, it is elongated first, and the girth increased subsequently (UKMoths). Yellow-brown to light grey tubular silken case with darker length lines. The case is fairly large (up to 17 mm) and very slender. The rear end is three-valved, the mouth angle about 50°. The larva feeds at the underside of the leaf (Bladmineerders van Europa).
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Coleophora peribenanderi Toll, 1943 [Lepidoptera: Coleophoridae].
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3a > Leaf-miner: The eggs of this species are laid on a leaf, with the larvae mining the underside of the leaf, until a late instar when it feeds in a web under the midrib of the leaf, causing visible blotching on the upperside (UKMoths). Short, full depth corridor. The larva relatively long lives as a miner, but finally leaves the mine and continues living in spinning along the midrib at the leaf underside, from where windows are eaten in the leaf (Bladmineerders van Europa).\
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Agonopterix propinquella (Treitschke, 1835) [Lepidoptera: Depressariidae].
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3b > 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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3c > Leaf-miner: The larva makes a large number of untidy full depth mines. The mines contain hardly or no frass. The opening made by the larva in the underside of the leaf is irregular roundish, sometimes more of a slit, large in proportion to the size of the mine, and usually positioned at the side of the mine. The larva mines until just before the pupation, that takes place externally (Bladmineerders van Europa).
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Jordanita globulariae (Hübner, 1793) [Lepidoptera: Zygaenidae].
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4c > Leaf-miner: The mine begins in the midrib, especially in a lower leaf, extending into the leaf disc, branching irregularly or pinnately, may also locally be blotch like. The mine is brown and very transparent. Sides very irregularly eaten out. Frass loosely dispersed or in a loose central line, buy may also be pressed against the sides of the corridor. The larva may also leave the mine and restart elsewhere (Bladmineerders van Europa).
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Orthochaetes setiger (Beck, 1817) [Lepidoptera: Curculionidae].
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4d > Leaf-miner: The larva makes a small full depth blotch, usually in the leaf tip. Frass concentrated in the centre of the mine The legless larva, when full grown, makes a globular cocoon in that same centre and pupates there (Bladmineerders van Europa).
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| Pseudorchestes pratensis (Germar, 1821) [Lepidoptera: Curculionidae]. |
| Last updated 04-Feb-2012 Brian Pitkin |  |
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