Robackia Sæther

Description

Introduction

Medium-sized larvae, up to 8 mm long.

Dorsal Head

Undescribed.

Antenna

Antenna 7 segmented with variable sclerotisation, basal segment shorter than segments 2 and 3 combined. Ring organ situated in basal 1/2 of basal segment. Blade arising on apex of 2nd segment, extending to 4th segment; accessory blade absent. Lauterborn organs absent. Large style present on apex of 5th segment. Antennal seta absent.

Labrum

SI and SII fine, seta-like, SII moderately long and broad, SIII very small, seta-like; SIVa long, 3-segmented. Labral lamellae absent. Pecten epipharyngis a small triangular plate. Premandible with 4 teeth, brush present.

Mandible

Mandible lacking dorsal tooth, with long apical tooth and 4 inner teeth, the innermost may be greatly expanded. Seta subdentalis very long, slender. Seta interna absent. Pecten mandibularis absent.

Mentum

Mentum with paired median teeth level with or slightly lower than first pair of lateral teeth, with 5-6 pairs of lateral teeth. Mentum unicolourous, pale to brown. Ventromental plates coarsely striate, as wide as mentum, with strongly crenate anterior margin. Setae submenti simple.

Maxilla

Palp very long, first segment 4 times as long as wide.

Body

Posterior parapods elongate, 6-7 times as long as basal width; claws simple. Procercus half as high as wide. Anal tubules conical, as long as parapods.

Notes

Taxonomic Notes

Robackia larvae differ from all other Chironomini, with the exception of Beckidia and Demicryptochironomus, in having 7 antennal segments. They may be distinguished from these 2 genera, as well as all others of the 'Harnischia' complex, by the slender, seta-like SII.

Keys

Saether (1977b) keys 2 of the 3 known species.

Ecological Notes

Larvae of Robackia inhabit sandy substrata in rivers, large streams and littoral of lakes.

The genus has a Holarctic distribution. Of three known species, one is Palaearctic (R. demeijerei) and two Nearctic (R. claviger and R. pilicauda).

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