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

1a > Leaf-miner: An irregular linear mine, which in small leaves can form a secondary blotch.

Long, upper-surface corridor, winding through the leaf and frequently crossing itself; in small leaves often a secondary blotch in the end. Frass in short strings and pearl chains. Pupation outside the mine.

An irregular gallery, sometimes crossing over, with black frass arranged as elongate very narrow streaks at the sides of the mine.

On Aster, Bellis and Solidago, but not yet on Xanthium, in Britain and additional genera of Asteraceae elsewhere. Widespread in Britain. Also recorded in the Republic of Ireland. Widespread and common in much of continental Europe.

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

1b > 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.

A linear mine on the upper surface, usually following the midrib and showing side branches along the veins. The frass is in strings.