Petasites butterbur

Dichotomous table for leafminers

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

1b mine upper- or lower-surface; larva a maggot => 3

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

2a mine not larger than 1 square cm, often a number in a leaf: Platyptilia gonodactyla*

2b mine larger, finally occupying a large part of the leaf: Scrobipalpula tussilaginis

3a primary and secondary feeding lines conspicuous; mine finally often blotchy; frass scattered irregularly; larva: rear spiraculum with 3 papillae => 4

3b no feeding lines visible; a definite corridor; frass in 2 rows;rear spiraculum with > 3 papillae => 6

4a corridor or narrow blotch, positioned over a thick vein: Trypeta zoe

4b corridor that opens into a large blotch, not associated with a vein => 5

5a first section of the mine is a hair-thin, not widening corridor which cuts off a section of the leaf, that thereby becomes necrotic; later a large blotch develops within the necrotic part: Stemonocera cornuta

5b corridor does not ring a part of the leaf, gradually widening into an untidy blotch: Acidia cognata

6a larva leaves the mine prior to pupation through an upper-surface semicircular exit slit; corridor gradually widening: Phytomyza tussilaginis

6b puparium in the mine; corridor not widening appreciably => 7

7a corridor upper-surface, greyish-green; frass in discrete grains: Chromatomyia cf. syngenesiae

7b corridor inter-parenchymal, yellow-green, extremely long (up to 20 cm!); frass in pearl chains: Phytomyza farfarae

*In more recent literature this species is not described as a miner.

Not included in the key: Phytomyza buhriella; Phytosciara halterata, macrotricha; Scrobipalpa pauperella; Scrobipalpopsis petasitis.

mod 9.x.2017