British Insects: the Odonata
Adults. Adults about 52–55–58 mm long (the male somewhat the longer). Average wingspan 72 mm; hindwings 34–37 mm long.
The eyes dorsally broadly contiguous; brown and green (female), or brown and blue (male).
Thorax very hairy. Legs black. Thoracic antehumeral stripes present (also humeral stripes, in the male), or absent (in the female); bright green. The wings spread more or less horizontally in repose; dissimilar in shape and venation; sessile; unpatterned and clear (in the male), or suffused with colour at their bases only, or suffused with colour basally and in the leading half, or suffused with colour basally and (in the forewings only) in a patch near the cubital point (being more or less tinted, in the female). The tinting in the female, amber. The inner wing venation blackish. Discoidal cell divided longitudinally into a conspicuous triangle and supra-triangle. Antenodal veins in the forewings about 12–16 (fewer in the hindwings); incorporating two conspicuously stronger primaries, and those in the costal and subcostal spaces unaligned. Pterostigma narrow-linear; light brown to yellow.
Abdomen rather stoutly linear from base to tip to linear from a conspicuously swollen base (more obviously swollen in the female, scarcely so in the male); 38–42 mm long (female), or 40–46 mm long (male); predominantly black (with yellow markings in the female, blue and yellow in the male); complexly patterned, or predominantly longitudinally lined (with an interrrupted, narrow blue median line in both sexes, the male with large paired blue spots and a narrow interrupted yellow band on each segment, the spots blue in the male and yellow in the female); with mid-dorsal spots. The male abdomen auriculate on segment 2; with a single inferior anal appendage.
Nymphs. The nymphs stout, the body expanded in the middle; when mature, 35–40 mm long.
The eyes small; lateral and widely separated on the top of the head. The head in dorsal view 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 7 segmented. The mask abruptly narrowed well before the hinge, with the prementum stalked to narrowed gradually to the hinge (the prementum tapering backwards to about halfway, then more or less straight to the hinge); with a flat prementum; with a short slit-like median cleft. Legs shorter than the abdomen; fore- and middle tarsi 3-segmented.
The abdomen terminating in five short spine-like appendages; gizzard with 4–8 folds.
Distribution. Northern England, English Midlands, East Anglia, Wales, southeast England, southwest England, Ireland, and central southern England (rare in northern England). Adults on the wing late April to late July (generally in best mature condition mid-May to mid-June).
Classification. Anisoptera; family Aeshnidae.
General comments. Exhibiting the hairiest thorax of all the British dragonflies.
Illustrations. • Brachytron pratense (from Lucas). • Brachytron pratense: nymph (from Lucas).
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’.