Lactuca lettuce

Dichotomous table for leafminers

Incl. Cicerbita, Mulgedium; see also Mycelis, that currently is incorporated in Lactuca.

1a mine full depth; larva with chitinised head => 2

1b mine upper- or lower-surface; larva a maggot => 4

1c galls, etc => Tables for all parasites per species

2a mine flat; larva apodous, light brown: Orthochaetes setiger

2b mine somewhat bulging; larva with feet, grey => 3

3a larva: pinacula colourless (the bases of the setae themselves are black) : Cnephasia incertana

3b pinacula black: Cnephasia stephensiana

4a upper-surface blotch without association with the midrib; often an initial corridor => 5

4b corridor mine, may be on, or sometimes in, the midrib => 9

5a the mine begins with a long or short gallery => 6

5b blotch from the first start: Liriomyza lesinensis

6a gallery section long and slender: Liriomyza serriolae

6b gallery section short, quickly widening => 7

7a frass concentrated in the centre of the blotch: Liriomyza scorzonerae

7b frass more or less evenly dispersed => 8

8a not uncommon on Lactuca: Liriomyza sonchi

8b rarely on Lactuca: Liriomyza endiviae

9a mine on or (partly) in the midrib => 10

9b mine not associated with the midrib => 15

10a midrib galled, swollen: Phytomyza penicilla

10b midrib not swollen => 11

11a mine pinnately branched; pupation after the mine has been vacated; frass in strings in the corridor and its side branches; larva: cephalic skeleton of the Phytomyzinae-type: Liriomyza strigata

11b larva lives in the midrib, from where it makes short exccursions into the lamina; these corridors almost free of frass, which is accumulated in the base of the hollow midrib; there also the puparium; larva: cephalic skeleton of the Agromyzinae-type => 12

12a full grown (3e stadium) larva: mandible with 1 tooth (check carefully: they alternate): Ophiomyia pinguis

12b full grown larva: mandible with 2 teeth => 13

13a mandibular teeth differ little in size; puparium black: Ophiomyia cunctata

13b lower tooth much smaller than the upper one; puparium yellow-brown => 14

14a larva: anterior spiraculum an erect spine with c. 14 papillae: Ophiomyia pulicaria

14b anterior spiraculum broader, curved, with c. 7 papillae: Ophiomyia beckeri

15b frass in discrete grains => 16

15a frass in strings => 18

16a puparium in the mine => 17

16b puparkium external; mine begins with an exceptionally long underside gallery: Phytomyza marginella

17a puparium usually in an underside pupal cradle; gallery with normal amounts of frass grains; highly polyphagous species: Chromatomyia cf. syngenesiae

17b puparium at the end of the gallery; gallery with unusually little frass; only known from Lactuca alpina: Chromatomyia griffithsiana

18a larva: rear spiraculum with 3 papillae; mostly in greenhouses: Liriomyza trifolii

19b rear spiraculum with ≥ 6 papillae => 19

19a usually the gallery begins lower-surface, then turns upper-surface (and then often forming a secondary blotch); mostly in the open air: Liriomyza bryoniae

19b usually the gallery begins upper-surface, then continues lower-surface; rarely a secondary blotch; mostly in greenhouses: Liriomyza huidobrensis

Not included in the key: Phytosciara halterata; Trypeta zoe.

mod 23.iii.2018