Potamogeton pondweed

Dichotomous table for leafminers

1a larva with a distinct, chitinised, head capsule => 2

1b larva a virtually headless maggot => 5

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

2a larva with three pairs of thoracic feet => 3

2b larva with one pair of short or long extensions (pseudopodia) on the first thoracic, and the last abdominal, segment (Chironomidae) => 4

3a the young larva makes a small blotch; later it lives in a case, made of leaf fragments: Elophila nymphaeta

3b the young larva sometimes bores in the stem or in the midrib: Acentria ephemerella (not a true miner)

3cthe young larva makes a long, narrow gallery: Nymphula nitidulata

4a the larva lives in a corridor (usually in dead plant material) with two openings, in which it maintains a water current by constant sinuous movements. It lives on detritus particles brought by the current. These larvae are no miners, and are not discussed here. Hering (1957a) keys the species known up to then.

4b the larva lives in a slender, rather deep gallery with only one opening, and feeds on living plant tissue: Cricotopus brevipalpis and the badly known Cricotopus obnixus

5 Mandible with 1 tooth, no anterior spiraculum: Hydrellia (Ephydridae). The larvae of several species make irregular, very shallow mines, both in the floating and in the submerged leaves. The larvae are not described, and the mines are not sufficiently diagnostic, so only rearing can lead to an identification. The larvae pupate in the mine, breeding therefore poses not many problems. The key of the adult flies that follows is entirely derived from Hering (1957a) => 6

5b anterior spiraculum present, mandible with more teeth: Scaptomyza griseola.

6a tibia of all feet reddish yellow, possibly with a black ring halfway: Hydrellia fascitibia

6b tibia of all feet black, possibly somewhat yellowish distally => 7

7a face white: Hydrellia maura

7b face yellow => 8

8a antenna reddish yellow (somewhat darkened in the males), arista with a row of 7-9 bristles: Hydrellia cochleariae

8b antenna entirely black => 9

9a at least the rear tarsi reddish yellow => 10

9b tarsi and coxae entirely black: Hydrellia fusca

10a coxae entirely black; arista with 8-10 bristles: Hydrellia albifrons

10b front coxae distally yellow; arista with 5-7 bristles: Hydrellia viridescens

mod 10.vii.2018