British Insects: the Odonata
Adults. Adults about 29–32–35 mm long. Average wingspan 39 mm; hindwings 15–20 mm long.
The eyes lateral and widely separated; blue. The front of the head immediately interior to the eyes not pale whitish blue (mostly black).
The prothorax posteriorly more or less entire. Hind tibia without a featherlike expansion. Thoracic antehumeral stripes present (humerals also conspicuous); blue (in both sexes). 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 elongated but only about about twice as long as wide. 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); 22–26 mm long; predominantly pale blue and black (in both sexes); in both sexes, segments 1 and 2 are dorsally complexly patterned black; 3, 4 and 5 are posteriorly patterned black, the black extending further forward in the female; and 6, 7 and 8 are black. 9 is blue with a posterior black band in the male, and black with a blue lateral spot on each side in the female; 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, 20–22 mm long.
The head without prominent spots; in dorsal view markedly narrowing from immediately 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 8–10 major setae (4+4 to 5+5, with no field of shrt setae proximal to them). The outer margins of the labial palps without spines. Distal margins of the labial palps crenate and coarsely toothed. 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; (shortly apiculate-) pointed; (apiculate-) with transverse dark bands; 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. Southeast England (known only from localities in Essex, where it may no longer exist). Adults on the wing late June to early August (generally in best mature condition late June to late July).
Classification. Zygoptera; family Coenagriidae.
General comments. Hindwings generally with one row of cells between the costa and the radius distal to the pterostigma; and the female without a strong ventral apical spine on segment 8.
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’.