Key for the identification of the known mines of British
insects (Diptera and non-Diptera) recorded on Urtica

1a > Leaf-miner: Larva forming linear-blotch mine between two veins, not adjoining margin of leaf, frass in distinct black strips or pellets (Spencer, 1972b: 37 (fig. 111), 39; Spencer, 1976: 100 (fig. 146)).

Full depth mine with indistinct primary and secondary feeding lines. Generally the mines lie in the centre of the leaf. The mine starts as a narrow corridor, strongly, 'intestine-like', wound (unless the mine lies near the leaf margin, in which case the first part of the corridor follows the leaf margin). Further on the corridor widens into an elongated blotch. Part of the frass in a long fine thread. In comparision with the other two Agromyza's on Nettle the mine is much clearer, less green-cloudy. Pupation outside the mine.

The mine starts away from the leaf edge usually and has a coiled intestine-like start; it has frass in long threads in the broader part of the mine.

On Urtica dioica in Britain. On Parietaria officinalis, Urtica dioica, Urtica pilulifera, Urtica radicans and Urtica urens elsewhere. Widespread in Britain. Also recorded in the Republic of Ireland. Widespread in continental Europe.

Agromyza anthracina Meigen, 1830 [Diptera: Agromyzidae].

2

2a > Leaf-miner: Larva forming an irregular elongate linear blotch mine, normally adjoining margin of leaf (Spencer, 1976: 137).

Forms a long blotch mine, which is usually adjacent to the edge of the leaf, which turns black.

Full depth corridor, mostly beginning at the leaf margin, and never starting with a closely set, intestine-like, number of curves. Further on the corridor considerably widens, mostly keeping close to the leaf margin. Often several larvae in a mine. Frass in lumps or short rods, never in long threads. Pupation outside the mine.

Puparium reddish brown

On Urtica dioica in Britain. On Urtica dioica and Urtica ilulifera elsewhere. Widespread and common in Britain. Also recorded in the Republic of Ireland. Widespread in continental Europe.

Agromyza pseudoreptans Nowakowski, 1964 [Diptera: Agromyzidae].

Full depth corridor that mostly starts near the leaf margin, and never begins with a series in close, intestine-like curves. Further on the corridor strongly widens, and usually remains close to the leaf margin. Often several larvae in a mine. Frass in lumps or short rods, never in long threads.

On Urtica dioica in Britain. On Urtica dioica, Cannabis, Humulus, Mentzelia and Parietaria elsewhere. Widespread in Britain and continental Europe. Also recorded in Canada.