Stictochironomus Kieffer

Description

Introduction

Large, red, up to 14 mm long.

Dorsal Head

Frontoclypeal apotome without frontal fenestra; labrum distinct, other labral sclerites disrupted.

Antenna

Antenna with 6 segments, with segments 2 and 3 sometimes short; Lauterborn organs alternate on 2nd and 3rd segment, placed on short pedestal, style on apex of 3rd segment. Ring organ in basal third to quarter of segment 1, seta absent. Blade shorter than flagellum, accessory blade half as long as segment 2.

Labrum

SI and SII plumose on both sides; SIII, SIVa and b and labral lamellae normal. Seta premandibularis simple. Pecten epipharyngis of three separate distally serrate scales. Premandible with 3 teeth and very strong brush.

Mandible

Mandible with broad base and narrow dark toothed part; with strong, dorsal tooth, long, standing distinct from apical tooth; with 2-3 inner teeth. Pecten mandibularis weak or absent. Seta subdentalis inserted on ventral surface, simple, long, slender, extending first inner mandibular tooth. Seta interna inserted on dorsal surface, strongly plumose, 4-branched.

Mentum

All teeth dark, with clearly demarcated ventromental component of four teeth, median pair shorter than outer; dorsomentum of six teeth on each side, with 1st smaller than 2nd laterals. Ventromental plates separated medially by width of the median four mental teeth. Ventromental plate weakly curved, with curved, smooth anterior margin, with continuous striae. Setae submenti simple.

Body

Lateral and ventral tubules absent.

Notes

Taxonomic Notes

Stictochironomus larvae may be identified from the following combination of characters: antenna with 6 segments and alternate Lauterborn organs; dorsal tooth of mandible dark, as are all of the mental teeth; 4 median teeth of mentum higher than the 6 pairs of lateral teeth, central pair much more slender and lower than outer pair.

Larvae with only 3 median teeth [cf. Chernovski (1949b), sub Stictochironomus "connectens" No. 2] may be aberrant specimens, in which l of the 2 small median teeth is reduced. Oliver et al. (1978a) figure under Stictochironomus sp. 3 a distinctly different larval mentum, in which both small central median teeth are completely absent.

Larvae living in sand generally have strongly worn mouthparts.

Ecological Notes

Larvae of Stictochironomus occur in profundal soft sediments or littoral sand of oligotrophic to mesotrophic lakes; also prevalent in sandy sediments of streams and slowly flowing rivers.

The genus is represented in the Nearctic by thirteen species and in the Palaearctic by about eight, in part identical, species; in need of revision. In addition there are six Afrotropical and one known Oriental species.

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