THUJA. Cedars. [Cupressaceae]

Two species of Thuja are recorded in Britain. Both are introduced and include Northern White-cedar (T. occidentalis) and Western Red-cedar (T. plicata).

No Diptera miners are recorded on Thuja in Britain.

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

Elsewhere one additional British non-Diptera miner is recorded on Thuja (see below).

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

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).

1# > Details unknown.

Recorded on Chamaecyparis, Cupressus and Juniperus, but not yet Thuja, in Britain and Cupressus and Thuja elsewhere. A species which appears to be on the increase. It is believed to have been introduced with the foodplant and first appeared in Essex in 1988. Since then there have been quite a number of records, mostly from the south-east of England. Widespread in continental Europe.

Gelechia senticetella (Hübner, 1817) [Lepidoptera: Gelechiidae]

1a > Oviposition on a young shoot. The larva penetrates a leaf, empties it, leaves it, often by making another hole in the epidermis, and starts a new mine. Older larvae bore in a twig. Pupation external. Mines twigs rurn brown and are dropped (Bladmineerders van Europa).

Mines of Argyresthia trifasciata on Thuja occidentalis Image: Willem Ellis (Bladmineerders van Europa)

Recorded on Chamaecyparis, Cupressocyparis, Juniperus and Thuja in Britain and elsewhere. Widespread in Britain and continental Europe.

Argyresthia trifasciata Staudinger, 1871 [Lepidoptera: Gelechiidae]