Demicryptochironomus Lenz

Description

Introduction

Medium-sized to large larvae, to 12 mm long.

Dorsal Head

Undescribed.

Antenna

Antenna 7 segmented, basal segment much shorter than flagellum, terminal segments small. Long blade arises on apex of segment 2, reaching subapex of flagellum, accessory blade absent. Lauterborn organs absent. Style on apex of 5th segment. Antennal seta absent.

Labrum

SI slender, seta-like; SII very long, blade-like, more than 2x as long as SI, SIII very small, seta-like; SIVa long, 3-segmented, with SIVb a separate peg. No chaetae. Labral lamellae absent. Pecten epipharyngis a serrate triangular scale divided into 3 lobes. Premandible with 4 strong teeth, brush absent.

Mandible

Mandible lacking dorsal tooth, with strong, elongate, apical tooth and 2 pointed inner teeth. Seta subdentalis short. Seta interna reduced to 2 lamellae. Pecten mandibularis comprising one broad lamella, the rest narrower.

Mentum

Mentum with pale rounded broad median area, flanked by 7 pairs of obliquely-arranged dark lateral teeth. Ventromental plates each at least as wide as mentum; rounded or tapering to point laterally. with fine striate, with smooth anterior margin. Setae submenti simple.

Maxilla

Palp elongate.

Body

Posterior parapod claws simple.

Notes

Taxonomic Notes

The combination of 7 segmented antenna and broad pale median tooth to the mentum flanked by 7 pairs of dark obliquely-orientated lateral teeth is characteristic of Demicryptochironomus, including subgenus Irmakia Reiss.

Ecological Notes

Larvae occur in lakes, streams and rivers in sandy and muddy substrata. They are predatory especially on oligochaetes.

The nominate subgenus Demicryptochironomus has Holarctic distribution, with 2 species described from the Nearctic and 2 from the Palaearctic, and 1 from the Afrotropical region. Judging by immature stages, several undescribed species exist in the USA. Subgenus Irmakia is diverse in China based on adults (Yan et al., 2005), and is present in Australia and south-east Asia.

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