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GNAPHALIUM. Cudweeds. [Asteraceae] |
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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. Only one Diptera miner, the agromyzid Ophiomyia gnaphalii, is recorded on Gnaphalium in Britain. The polyphagous agromyzid Liriomyza trifolii has been recorded in quarantine in Britain (Pitkin and Plant in British leafminers). Elsewhere the agromyzids Calycomyza artemisiae, Chromatomyia horticola, Liriomyza sativae, Liriomyza strigata, Liriomyza trifolii and Ophiomyia gnaphalii are recorded mining Gnaphalium. No non-Diptera miners are recorded on Gnaphalium in Britain. Elsewehere one British non-Diptera miner is recorded on Gnaphalium (see below). A key to the European miners, based on characteristics of the mines, immature stages and where relevant the larval cases, recorded on Gnaphalium is provided in Bladmineerders van Europa. This includes Chromatomyia cf. syngenesiae, Ophiomyia gnaphalii, Phytomyza kyffhusana, Liriomyza strigata, Digitivalva reticulella and Orthochaetes insignis. |
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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 > Leaf-miner: An external stem mine or leaf mine in basal leaves (Bland, 1999). In the latter case 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 stem mine of Gnaphalium or among basal leaves of Antennaria.
Ophiomyia gnaphalii Hering, 1949 [Diptera: Agromyzidae]. |
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Key for the identification of the mines of British
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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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1 > 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 legless 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. (Bladmineerders van Europa).
Orthochaetes insignis (Aube, 1863) [Coleoptera: Curculionidae] |
| Last updated 05-Feb-2012 Brian Pitkin |  |
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