British Insects: the Odonata
Adults. Adults about 28–31–34 mm long. Average wingspan 40 mm; hindwings 17–22 mm long.
The eyes lateral and widely separated; brown and green, or brown and blue. The front of the head immediately interior to the eyes not pale whitish blue (mostly black).
The prothorax posteriorly more or less entire. Legs not red. Hind tibia without a featherlike expansion. Thoracic antehumeral stripes present (the humeral stripes also conspicuous); blue (in the male), or green (in the female). 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 more or less isodiametric. 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); 24–26 mm long; predominantly blue and black (in the male), or green and black (in the female); in the male, segment 2 is complexly patterned, while segments 3 to 7 and 10 are entirely or posteriorly black; while in the female, all but segments 1 and 2 of the abdomen is mostly black, with narrow green intersegmental bands; without mid-dorsal spots. Abdominal segment 2 of the male blue, with a more or less spear-shaped but variable dorsal black mark joined to the black posterior circlet, and consistently exhibiting a black line on either side. 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, 21–23 mm long.
The head with prominent spots; in dorsal view markedly narrowing from immediately behind the eyes. The antennae 6 segmented; with the scape considerably shorter than the other segments taken together; with the first flagellar segment longer than the pedicel. The mask abruptly narrowed well before the hinge, with the prementum stalked, or narrowed gradually to the hinge (Gardners Fig. 6b shows a narrow-elongate labium, not in the least triangular like that of the other species of Coenagriidae illustrated); without a median cleft. The prementum bearing 6–10 major setae (3+3 to 5+5). The body of the labial palps bearing 5–7 major setae. The outer margins of the labial palps without spines. 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 oblanceolate; pointed; hyaline without coloured markings; hairy on both margins to beyond the middle; 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. Northern Scotland. Adults on the wing late may to early August (generally in best mature condition mid-June to late July).
Classification. Zygoptera; family Coenagriidae.
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’.