Identifying leafmines

Apart from Agromyzidae and other leafmining flies, the larvae of other insects also feed within the leaves and stems of plants. The larvae of beetles (Coleoptera), moths (Lepidoptera) and sawflies (Hymenoptera) can be found to be feeding on plant tissue in the same manner as Agromyzidae.

However, when a larva(e) is present within a mine, it is relatively straightforward to differentiate between the four groups of leafminers.

Coleoptera

The larvae of beetles have chewing moutparts with opposite mandibles as part of their head capsule, which Diptera larvae do not possess. In most species, the larvae have at least six thoracic legs, however, they can be absent or reduced in some species. Beetle larvae do not have any abdominal legs.

Diptera

The larvae of leafmining flies are maggots, with no legs or eyes. There is no head capsule. Diptera larvae never possess abdominal or thoracic legs. They also lack chewing mouthparts, however, they do have a characteristic, often obvious, cephalo-pharyngeal skeleton which can usually be seen through the body wall. In order to feed, the larvae use their pick-like mouthparts to scrape away at the plant tissue - the below video shows this in action;

Hymenoptera

Sawfly larvae, like beetle larvae, have at least six thoracic legs, which may be almost absent or reduced in size. The majority of species also have up to six pairs of prolegs (abdominal feet) but these may be extremely reduced in size. They also possess a head capsule which incorporates the chewing mouthparts and opposite mandibles.

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Larvae of the Sawfly, Parna apicalis, showing the prothoracic feet, head capsule and opposite mandibles.

Even when in the mine, the larva can be seen to clearly possess prothoracic feet, ruling out a dipterous species;

Lepidoptera

Similarly to beetle and sawfly larvae, moth larvae have at least six thoracic legs, a head capsule and chewing mouthparts. There are never more than 5 pairs of prolegs. The head is often retracted into the pronotum and therefore can be difficult to see.


Host plant

Knowing the host plant when trying to identify a leafminer is a crucial aid in identification and can, in some cases, allow an immediate determination.

Most Agromyzidae are restricted to a single species of plant or to a few which are very closely related (same genus). These type of leafminers, which feed solely on one species of plant, are called monophagous. Ones which utilise several species of plant which are not very closely related are referred to as Oligophagous. In some instances, some species are polyphagous, meaning they feed on a wide range of unrelated plant species. An example of this is Liriomyza strigata, which has been recorded on 15 plant families in Britain.

The 'host plants' section lists host plants and which species of Agromyzidae have been recorded on that genus/species. New host plants are being recorded each year and therefore, the information on this website will be updated whenever possible.