HYDROCOTYLE. Pennyworts. [Apiaceae]

Marsh Pennywort or White-rot (H. vulgaris) is the only native species of Hydrocotyle recorded in Britain. Four other species have been introduced, including Hairy Pennywort (H. moschata), New Zealand Pennywort (H. novae-zeelandiae) and Floating Pennywort (H. ranunculoides).

Only one Diptera miner, Liriomyza strigata, is recorded on Hydrocotyle in Britain.

The polyphagous agromyzid Liriomyza trifolii has been recorded in quarantine in Britain (Pitkin and Plant in British leafminers).

Elsewhere the polyphagous agromyzids Liriomyza bryoniae, Liriomyza sativae, Liriomyza trifolii and Liriomyza strigata are recorded mining Hydrocotyle.

No non-Diptera miners are recorded on Hydrocotyle in Britain.

A key to the European miners, based on characteristics of the mines, immature stages and where relevant the larval cases, recorded on Hydrocotyle is provided in Bladmineerders van Europa. This includes Liriomyza strigata but not Liriomyza bryoniae, Liriomyza sativae or Liriomyza trifolii.

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: 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).

On more than 40 host genera in 15 families in Britain including Hydrocotyle. Widespread throughout Britain. Also recorded in the Republic of Ireland. Widespread in continental Europe.

Liriomyza strigata (Meigen, 1830) [Diptera: Agromyzidae].