Acalcarella Shilova

Description

Introduction

Moderate-sized larvae, to 5.5 mm long.

Dorsal Head

Not described.

Antenna

Antenna with 5 segments, 1/4 long as length of head, basal segment as long as flagellum (AR c 1.0). Ring organ in proximal 1/4 of 1st antennal segment. Blade arising distally on the basal segment, extending to, or substantially beyond apex of antenna. Lauterborn organs lacking. Antennal seta absent. Style absent.

Labrum

SI seta simple, blade-like; SII elongate, robust blade, 2x length of SI, flanked by a long. blade-like chaeta; SIII simple, seta-like; SIVa 3-segmented, elongate. Labral lamellae absent. Pecten epipharyngis a single, triangular scale, divided into 2 or 3 lobes distally. Premandible with 4-5 teeth, apical 2 much longer than proximal ones, brush present.

Mandible

Mandible lacking dorsal tooth, apical and 3 inner teeth pale yellow. Seta subdentalis slender, extending to subapical tooth. Seta interna of 4 branches, distal 2 serrate on 1 margin, other 2 simple.

Mentum

Mentum normally dark to quite pale, median tooth wide, triangular, flanked by 6-7 pairs of lateral teeth on even line of slope. Ventromental plates 2.5-3.0 times as wide as high, with distinct striae, gently curved, with serrate anterior margin.

Maxilla

Palp elongate.

Body

Two pairs of anal tubules, well developed in Canadian specimens, apparently vestigial in Russian specimens.

Notes

Taxonomic Notes

The generic diagnosis was based originally on material from Canada, collected by Wiens et al. (1975) and on the published description of A. nucus by Shilova (1955). This is supplemented by examination of new material from Lake Superior in North America. The scale-like triangular pecten epipharyngis, divided into a few points apically, and the mentum with a wide triangular median tooth are together sufficient to distinguish larvae of Acalcarella from all other Chironomini.

Ecological Notes

Little information were available; the only two records are from the Amu-Darya drainage basin (U.S.S.R.) and Shell Lake in the Mackenzie River delta (Canada). Records now include Lake Superior in North America.

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