British Insects: the Odonata

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L. Watson and M. J. Dallwitz

Somatochlora arctica (Zetterstedt, 1840)

Northern Emerald Dragonfly.

Adults. Adults about 46–50–54 mm long. Average wingspan 68 mm; hindwings 32–36 mm long.

The eyes dorsally narrowly apposed to dorsally broadly contiguous; green (in both sexes).

Legs black. Thoracic antehumeral stripes absent. The wings spread more or less horizontally in repose; dissimilar in shape and venation; sessile; suffused with colour at their bases only (in the female), or colour tinted throughout (and darker towards their bases, in the male). The tinting amber. The inner wing venation blackish. Discoidal cell divided longitudinally into a conspicuous triangle and supra-triangle. Antenodal veins in the forewings about 7–10 (fewer in the hindwings); without distinct primaries, and those in the costal and subcostal spaces more or less aligned. Pterostigma well over twice but no more than five times as long as wide; dark brown (to blackish brown, in the male).

Abdomen robustly linear from base to tip to linear from a conspicuously swollen base (in the female), or swollen both basally and distally and markedly constricted in between (in the male, the constriction involving several segments forward of the middle); 37–40 mm long; predominantly dull bronze black; non-metallic; almost plain (with paired large, lateral orange spots on segment 3 in the female, these lacking in the male); without 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, 17–22.5 mm long.

The antennae 7 segmented. The mask having the prementum hollowed dorsally. The prementum bearing 18–28 major setae (9+9 to 14+14). The body of the labial palps bearing 7–9 major setae. Distal margins of the labial palps strongly crenate. Legs longer than the abdomen.

The abdomen terminating in five short spine-like appendages. The cerci more than half the length of the paraprocts. The abdomen without mid-dorsal spines; gizzard with 4–8 folds.

Distribution. Northern Scotland and Ireland. Adults on the wing late may to early August (generally in best mature condition mid-June to late July).

Classification. Anisoptera; family Corduliidae.

Illustrations. • Somatochlora arctica and S. metallica (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’.

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