THYMUS. Garden Thymes. [Lamiaceae]

Six species and subspecies of Thymus are recorded in Britain. These include the native Wild Garden Thyme (T. polytrichus).

No Diptera miners are recorded on Thymus in Britain.

Four non-Diptera miners are recorded on Thymus in Britain, although two of these require confirmation.

The coloephoorid Coleophora lixella is recorded as a seed-feeder on Thymus in Britain (see below).

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

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 > 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)

2

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

3

2a > Leaf-miner and case-bearer: Blotch mines reaching the edge of the leaf, initially pale green turning brownish white, are caused by the larva feeding on the underside of a leaf (UKMoths). The fully developed case is slender, shining black brown, about 9 mm long. Towards the end a narrow, transparent yellowish ventral keel. Mouth angle 50-60°. Cases on the leaf underside (Bladmineerders van Europa).

Recorded on Calamintha, Clinopodium, Glechoma, ? Lycopus, Mentha, Nepeta, Origanum, Prunella, Salvia, Stachys and Thymus in Britain plus Melissa, Melittis and Satureja but not Calamintha elsewhere. Throughout England and Wales and a few places in Scotland. Widespread in continental Europe.

Coleophora albitarsella Zeller, 1849 [Lepidoptera: Coleophoridae].

2b > Leaf-miner and case-bearer: Larva in a slender, brownish black, bivalved sheath case of 7-8 mm. The oral half is tubular, the rear part strongly laterally compressed. Mouth angle 30°. Actually the case only looks like a sheath case. The larva cuts off mined leaves, after having removed the complete leaf margin: what is left is an upper and a lower epidermis, connected by the stub of the petiole. Leaves treated in this way are placed in front of the old case, the stub dorsally, and pointing forwards. The stubs together form a low dorsal keel. The case in fact is a composite leaf case. However, the larva adds so much silk (also because the leaves are too small to form a complete tube) the the leaf fragments are obliterated (Emmet et al., 1996a) (Bladmineerders van Europa).

Recorded on Thymus in Britain and elsewhere. Britain including East Kent, North Hants and Surrey. Widespread in continental Europe.

Coleophora niveicostella Zeller, 1839 [Lepidoptera: Coleophoridae].

2c > Leaf-miner and case-bearer: Larva in an untidy composite leaf case of c. 9 mm with a mouth angle of 90°. The larva mines a leaf, usually at the top of a twig, completely out, often while attached to the leaf margin. When the leaf is emptied it is cut off and forms the newest addition to the case (Bladmineerders van Europa).

Recorded on Thymus in Britain and elsewhere. Britain including Caernarvon, East Kent and West Cornwall. Widespread in continental Europe.

Coleophora serpylletorum Hering, 1889 [Lepidoptera: Coleophoridae].

3 > Leaf-miner: Young larvae make small, brown, full depth blotch mines without frass in the young leaves, from within the protection of a spinning. Later they cause upper-surface window feeding, while hidden among spun leaves (Bladmineerders van Europa).

Recorded on Thymus in Britain and Mentha, Thymus and Satureja elsewhere. Widespread in Britain and continental Europe. Also recorded in Ireland.