Zinnia [Asteraceae] in Leaf and stem mines of British flies and other insects

The leaf and stem mines of British flies and other insects

(Coleoptera, Diptera, Hymenoptera and Lepidoptera)

by Brian Pitkin, Willem Ellis, Colin Plant and Rob Edmunds

ZINNIA. Zinnias. [Asteraceae]

Two introduced species of Zinnia are recorded in Britain.

Four British miners are recorded on Zinnia.

A key to the European miners recorded on Zinnia is provided in Bladmineerders van Europa.

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

1a > Leaf-miner: A short linear mine in first instar, later producing a circular or oval blotch. Frass is excreted in a black mass prior to pupation; puparium firmly glued with frass within the mine (Spencer, 1976: 306).

Large, whitish, upper-surface blotch, preceded by a short corridor that often is overrun later by the developing blotch. The larva hardly produces any frass; the few grains that are present are black and rather coarse. But when the larva is about to pupate, it empties its intestine, which has the effect that the puparium is anchored in the mine by dried frass.

The initial gallery by the first instar larva then leads to a whitish blotch. The puparium is fixed to the inside of the mine by an accumulation of frass.

On Aster, Bellis and Erigeron, but not yet on Zinnia, in Britain and additional genera of Asteraceae elsewhere. Widespread in southern England and continental Europe. Also recorded in Canada, Argentina, South Africa, India, Australia and Papua New Guinea.

Calycomyza humeralis (von Roser, 1840) [Diptera: Agromyzidae].

1b > Leaf-miner: Mine linear, whitish, both upper and lower surface. Pupation internal, at the end of the mine with the anterior spiracles projecting through the epidermis (Spencer, 1976: 433).

Upper-surface, less often lower-surface corridor. Frass in isolated grains. Pupation within the mine, usually in a lower-surface puparial chamber.

A long whitish upper surface corridor, which eventually goes lower surface.

Two highly polyphagous species of Chromatomyia, with indistinguishable mines, have been recorded in Britain. These are syngenesiae (Hardy) and horticola (Goureau) which can only be distinguished by the male genitalia. Both species are widespread in Britain and elsewhere, although syngenesiae is almost entirely restricted to Asteraceae. Records on Asteraceae not based on examination of male genitalia are treated in this account as Chromatomyia 'atricornis'.

Chromatomyia syngenesiae is recorded on Zinnia elsewhere but not yet on Zinnia in Britain.

Chromatomyia syngenesiae Hardy, 1849 [Diptera: Agromyzidae].

1c > 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.

Liriomyza strigata larva, lateral Image: © Willem Ellis (Bladmineerders van Europa)
Polyphagous. On more than 40 host genera in 15 families, but not yet on Zinnia, in Britain and elsewhere. Widespread throughout Britain. Also recorded in the Republic of Ireland. Widespread in continental Europe.
*Liriomyza strigata* (Meigen, 1830) [Diptera: Agromyzidae].
1d > Leaf-miner: In the first instar the larva mines the leaves, forming short, irregular, blotch-like mines, but in later instars it lives externally, feeding in spun leaves and often twisting those of tender shoots. Larval head light-brown or yellowish brown, edged with black postero-laterally, ocellar area blackish; prothoracic plate black edged with whitish anteriorly; abdomen dull dark green; pinacula distinct, black, sometimes brownish but with black bases to setae; anal plate large, black (Bradley et al., 1973). Small, full depth mine without a definite shape; little frass. Some silk is deposited in the mine. The larva soon leaves the mine and continues feeding among spun leaves.
Polyphagous. On numerous genera and species of several plant families, but not yet on Zinnia, in Britain. On numerous genera and species of several plant families, including Zinnia, elsewhere. Widespread in Britain and continental Europe. Also recorded from the Channel Is.
Cnephasia incertana (Treitschke, 1835) [Lepidoptera: Tortricidae].


	Last updated 13-Feb-2018 Brian Pitkin