Pseudochironomus Malloch

Description

Introduction

Medium sized to large, red, up to 11 mm long. Head capsule evenly golden to brown with darker brown gula, mentum and apical mandibular tooth. Occipital margin darkened.

Dorsal Head

SIII seta on separate clypeus anterior to frontal apotome.

Antenna

Antenna with 5 segments. Ring organ near base of segment 1, seta absent. Blade extending to near apex of antenna, accessory blade long. Lauterborn organs opposite on apex of 2nd segment. Style about half length of segment 3.

Labrum

SI and SII plumose, SII weakly so; SIII simple, short; SIVa and b short. Seta premandibularis strong and simple. Labral lamellae broad, without indication of median division, with 15-30 teeth. Pecten epipharyngis of three simple scales. 10-12 apically plumose chaetulae laterales, 2 apically branched chaetulae basales. Premandible with 2 teeth and strong brush.

Mandible

Dorsal tooth absent, with pale apical tooth and 4 dark inner teeth. Pecten mandibularis absent. Seta subdentalis inserted on dorsal surface, long, curved extending to near apical mandibular teeth. Mola and inner margin smooth. Seta interna inserted on dorsal surface, strongly plumose, 4-6-branched.

Mentum

Mentum with no distinct ventromental component, simple, broad, rounded median tooth, slightly more protruding 1st laterals, reduced 2nd laterals, and remaining 4 laterals evenly sloping. Ventromental plates slender and scarcely separated medially. Ventromental plate subequal to or wider than width of mentum, densely striate. Setae submenti simple.

Body

Lateral and ventral tubules absent. Anterior parapods with dense, fine, simple claws; posterior parapod claws simple.

Notes

Taxonomic Notes

Pseudochironomus larvae are distinguished by the slender ventromental plates, which are almost in contact medially and which possess a narrow central band of fine striae. In this respect they resemble Tanytarsini larvae. In addition the mandible has a pale apical tooth and the seta subdentalis is inserted on the inner side of the mandible. In all other Chironomini the apical tooth of the mandible is at least as dark as the inner teeth and the seta subdentalis is inserted on the outer side of the mandible.

Pseudochironomus is the only representative of the tribe Pseudochironomini in the northern hemisphere. The other genera, e.g. Riethia Kieffer and Manoa Fittkau occur in the southern hemisphere. The characters of Pseudochironomini larvae are insufficiently known. It is probable, therefore, that some of the characters given for Pseudochironomus have tribal, rather than generic significance. This is certainly so for the absence of pecten mandibularis and the structure of the ventromental plates. The diagnosis is thus valid only for the northern hemisphere. The larval mode of life, in sand, usually leads to badly worn mouthparts.

Keys

Key to larvae of known Holarctic Pseudochironomus species in Saether (1977b).

Ecological Notes

Larvae of Pseudochironomus favour sandy or gravelly littoral sediments, primarily in meso- to oligotrophic lakes or in large, slowly flowing rivers.

The genus is Holarctic-Neotropical in distribution, with one or two species in the Palaearctic, about eleven species in the Nearctic and at least five species in the Neotropical region.

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