British Insects: the Odonata
Pyrrhosoma tenellum, Palaeobasis tenellum.
Small Red Damselfly.
Adults. Adults about 27–31–34 mm long. Average wingspan 36 mm; hindwings 15–21 mm long.
The eyes lateral and widely separated; brown to red (reddish brown).
Legs pale red. Legs pale pale red. Thoracic antehumeral stripes present (usually, in the female), or absent; when present, yellow (-ish, and slender). The wings held vertically in repose; similar in shape and venation; petiolate; unpatterned and clear. The inner wing venation blackish. Discoidal cell a simple quadrilateral, not longitudinally divided (trapezoid, without transverse veinlets). The wings exhibiting 3 postquadrilateral cells between the quadrilateral cell and the subnodus. Antenodal veins in the forewings 2. Pterostigma reddish brown, or red. The hindwings with only one row of cells distal to the pterostigma between the costa and the radial vein.
Abdomen linear from base to tip (very slender); 23–26 mm long; predominantly bronze, or black (dark or blackish bronze in the female), or red (in the male); plain, or predominantly transversely banded (variously red with thin black and/or yellow inter-segmental bands, or the segments mostly black with yellow intersegmental bands); without mid-dorsal spots. The male abdomen without auricles on segment 2; with paired inferior anal appendages. Abdominal segment 8 of the female without a ventral apical spine.
Nymphs. The nymphs elongate and slender-bodied, gradually tapering posteriorly; when mature, 16–17 mm long.
The head in dorsal view not markedly narrowing from immediately behind the eyes. The postocular lobes curving sharply to the back of the head from some distance behind the eyes. The antennae with the scape considerably shorter than the other segments taken together; with the first flagellar segment longer than the pedicel. The mask narrowed gradually to the hinge; without a median cleft. The prementum bearing 2 major setae (usually, 1+1), or 4 major setae (less often 2+2). The body of the labial palps bearing 6 major setae. The outer margins of the labial palps without spines. Distal margins of the labial palps crenate and coarsely toothed (with one large, curved inner tooth, and the crenate but nearly entire part armed with setae). The moveable hooks of the labial palps without setae. The apical combs of the tibiae mainly of trifurcated setae.
The abdomen terminating in three conspicuous caudal gills. The three caudal appendages all lamellar. The caudal lamellae broadly oblanceolate; (apiculate-) pointed; blotched around the distal margins; with one margin hairless beyond the middle, the other hairy to nearer the apex; nodate, with the marginal hairs coarser proximally to the node and finer beyond it; with much-branched primary tracheal branches leaving the main trunk at an upward angle. The gizzard with 8–16 radially symmetrical folds.
Distribution. English Midlands, East Anglia, Wales, southeast England, central southern England, and southwest England (but very local in East Anglia). Adults on the wing late may to early September (generally in best mature condition late June to mid-August).
Classification. Zygoptera; family Coenagriidae.
General comments. Adults of both sexes with pale red legs.
Illustrations. • Ceriagrion tenellum (from Lucas). • Ceriagrion tenellum: B. Ent. 732. • Ceriagrion tenellum: B. Ent. 732, legend+text. • Ceriagrion tenellum: B. Ent. 732, text cont.. • Ceriagrion tenellum (female): Stephens VI, 1835. • Pyrrhosoma and Ceriagrion? (from Shaw and Nodder, about 1801).
To view the illustrations with detailed captions, go to the interactive key. This also offers full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, and distributions of character states within any set of taxa.
Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 2003 onwards. British insects: Dragonglies and Damselflies (Odonata). Version: 1st January 2012. http://delta-intkey.com’.