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AMARANTHUS. Pigweeds. [Amaranthaceae] |
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Thirty-three species of Amaranthus are recorded in Britain, all of them introduced. They include White Pigweed (A. albus), Prostrate Pigweed (A. blitoides), Guernsey Pigweed (A. blitum), Indehiscent Amaranth (A. bouchonii), Cape Pigweed (A. capensis), Love-lies-bleeding (A. caudatus), Purple Amaranth (A. cruentus), Perennial Pigweed (A. deflexus), Short-petalled Pigweed (A. graecizans), Green Amaranth (A. hybridus), Prince's-feather (A. hypochondriacus), Dioecious Amaranth (A. palmeri), Powell's Amaranth (A. powellii), Mucronate Amaranth (A. quitensis), Common Amaranth (A. retroflexus), Indehiscent Pigweed (A. standleyanus) and Thunberg's Pigweed (A. thunbergii). No Diptera miners are recorded on Amaranthus in Britain. The drosophilid Scaptomyza graminum is recorded on Amaranthus by Chandler (1978), but it is not clear whether the host association is British or Foreign. Elsewhere, in addition to the drosophilid Scaptomyza graminum, the agromyzids Amauromyza chenopodivora, Chromatomyia horticola, Liriomyza bryoniae, Liriomyza huidobrensis, Liriomyza sativae, Liriomyza strigata and Liriomyza trifolii and the anthomyiid Delia echinata are recorded mining Amaranthus. No non-Diptera miners are recorded on Amaranthus in Britain. Elsewhere two British non-Diptera miners, Chrysoesthia drurella and Chrysoesthia sexguttella, are recorded on Amaranthus (see below). A key to the European miners, based on characteristics of the mines, immature stages and where relevant the larval cases, recorded on Amaranthus is provided in Bladmineerders van Europa. This includes Amauromyza chenopodivora, Chromatomyia horticola, Delia echinata, Liriomyza bryoniae, Liriomyza strigata, Scaptomyza graminum, Chrysoesthia drurella and Chrysoesthia sexguttella but not Liriomyza huidobrensis, Liriomyza sativae or Liriomyza trifolii. |
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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: Oviposition can take place in the leaf, where a short mine is formed. The young larva feeds towards the mid-rib and down into the stem. Alternatively a true mine can be formed in the stem before the larva burrows deeper into the pith. Pupation external. Puparium yellow
Amauromyza chenopodivora Spencer, 1971 [Diptera: Agromyzidae]. 1b > Leaf-miner: A long, narrow, winding corridor running towards the midrib, widening to a blotch. Pupation usually in the soil, less often in the leaf (and then generally not in the mine itself but in a small separated mine, that may even be made in the petiole) |
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Scaptomyza graminum (Fallén, 1823) [Diptera: Drosophilidae]. |
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Key for the identification of the mines of British non-Diptera 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 > Leaf-miner: The larvae feed by mining the leaves forming a contorted gallery (UKMoths). A strongly contorted, often intestinine-like corridor, often forming a secondary blotch. Much green frass in broad arcs. Full grown larva mostly on top of the midrib. Pupation external (Bladmineerders van Europa).
Chrysoesthia drurella (Fabricius, 1775) [Lepidoptera: Gelechiidae]
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1b > Leaf-miner: Whitish blotches in the leaves (UKMoths). The mine begins as a short zigzagging corridor, that very soon becomes overrun by a large, perfectly transparent blotch. Frass in a big black central lump. In fresh mines something like primary feeding lines are recognisable, normally seen only in Diptera mines. Pupation external, exit a rather untidy hole (Bladmineerders van Europa). A large, whitish blotch sometimes occupying most or all of the leaf. The frass is mostly ejected from the mine. (British leafminers).
Chrysoesthia sexguttella (Thunberg, 1794) [Lepidoptera: Gelechiidae] |
| Last updated 03-Feb-2012 Brian Pitkin |  |
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