Geranium [Geraniaceae]

GERANIUM. Herb Robert and Crane's-Bills. [Geraniaceae]

Thirty-six species of Geranium are recorded in Britain, twelve of which are native.

Wood Crane's-bill (G. sylvaticum) is protected in Northern Ireland under Schedule 8 of the Wildlife (Northern Ireland) Order, 1985.

Only one Diptera miner, the agromyzid Agromyza nigrescens, is recorded on Geranium in Britain.

Elsewhere the agromyzid Agromyza nigrescens is recorded mining Geranium.

One non-Diptera leaf-miner is recorded on Geranium in Britain (see below).

Elsewhere two British non-Diptera miners are recorded on Geranium (see below).

A key to the European miners, based on characteristics of the mines, immature stages and where relevant the larval cases, recorded on Geranium is provided in Bladmineerders van Europa. This includes Agromyza nigrescens, Apterona helicoidella, Aricia agestis, Habroloma geranii, Fenella minuta, Fenella monilicornis and Orthochaetes insignis.

Crane's-bill
Geranium sp.

Key for the identification of the mines of British Diptera recorded on
Geranium

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: Initially a narrow linear mine which after first moult widens into large linear or irregular blotch; frass in distinct rows in the early linear section, later more scattered. Puparium reddish brown; posterior spiracles each with 3 spiracular pores.

On Geranium in Britain and Geranium and Erodium elsewhere. Widespread in Britain and continental Europe.

Agromyza nigrescens Hendel, 1920 [Diptera: Agromyzidae].

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

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).

1a > 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).

Recorded on Agrimonia, Fragaria, Geum, Potentilla and Rubus, but not yet on Geranium, in Britain plus Geranium elsewhere. Widespread in Britain and continental Europe.

Stigmella aurella (Fabricius, 1775) [Lepidoptera: Nepticulidae]

1b > 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).

Host plants unknown in Britain. Recorded on numerous genera and species in several plant families, including Geranium, elsewhere. Recorded in southern England. Widespread in continental Europe.

Orthochaetes insignis (Aube, 1863) [Coleoptera: Curculionidae]


	Last updated 05-Feb-2012 Brian Pitkin