Virgatanytarsus Pinder

Description

Introduction

Small larvae, up to 5 mm long.

Dorsal Head

Dorsal surface of head smooth. S3 setae always simple.

Antenna

Antenna 5 segmented, placed on tall pedestal without apical tooth or spur; basal segment longer than flagellum with proximal ring organ, moderately strong seta in distal 1/2 and blade extending to tip of segment 2; accessory blade very short, basally fused with blade; segment 2 distinctly longer than segment 3, more or less cylindrical or slightly wedge-shaped, bearing style and opposite Lauterborn organs distally. Lauterborn organs moderately large, placed on pedicels 1.5– 2.5x as long as segments 3–5 combined.

Labrum

S I comb-like, bases fused; S II distally plumose, situated on tall pedestal; S III simple, seta-like; S IV present. Labral lamella well developed. Pecten epipharyngis consisting of 3 distally serrated scales. Premandible with 5 teeth, including very slender lateral tooth; brush well developed.

Mandible

With dorsal tooth, apical tooth and 3 inner teeth, all brown. Seta subdentalis long, slender, reaching more or less to apex of mandible. Seta interna consisting of 4 plumose branches. Pecten mandibularis with up to 20 strong lamellae.

Mentum

Median tooth rounded or pointed, not notched or crenate laterally, slightly paler than or similar in colour to 5 pairs of lateral teeth. Ventromental plates very close together medially, 1.1–1.2x width of mentum.

Body

Posterior parapods with some very characteristic claws which bear a pad or row of very strong hooklets in addition to usual simple hooks.

Notes

Taxonomic Notes

Virgatanytarsus corresponds with Reiss and Fittkau’s (1971) triangularis group, in which all 3 developmental stages are distinct in some degree from Holarctic members of other chironomid genera. Larvae are characterized by the presence of combs or pads of small hooklets among the simple claws of the posterior parapods. However, this character is also observed in some Australian Tanytarsus larvae (Cranston, 2000b) is therefore not unique to Virgatanytarsus species in all geographical regions. Similar observations are made for the characteristic postero-lateral comb on the pupal abdominal segment VIII (Cranston, 2000b) and it is not unlikely that future phylogenetic analysis will find both Tanytarsus and Virgatanytarsus paraphyletic.

Ecological Notes

Larvae of Virgatanytarsus are known from small rivers and the littoral of lakes, living on stony substrata and on submerged macrophytes.

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