British Insects: the Odonata

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L. Watson and M. J. Dallwitz

Aeshna caerulea (Ström, 1783)

Azure Hawker Dragonfly.

Adults. Adults about 57–62–67 mm long (the female 58–64 mm). Average wingspan 80 mm; hindwings 38–41 mm long.

The eyes dorsally narrowly apposed to dorsally broadly contiguous; grey (or blue-ish, in females), or blue (in males).

Legs black. Thoracic antehumeral stripes present (these short, narrow and reduced, or absent, in the male), or absent (in the female); when present, azure blue. The wings spread more or less horizontally in repose; dissimilar in shape and venation; sessile; unpatterned and clear. The inner wing venation blackish. Discoidal cell divided longitudinally into a conspicuous triangle and supra-triangle. Antenodal veins in the forewings about 18–20 (fewer in the hindwings); incorporating two conspicuously stronger primaries, and those in the costal and subcostal spaces unaligned. Pterostigma well over twice but no more than five times as long as wide; black to dark brown (nearly black, in the male), or dark brown (in the female).

Abdomen linear from a conspicuously swollen base (briefly somewhat constricted adjoining the swelling, in the male); 42–44 mm long (female), or 45–48 mm long (male); predominantly dark brown (with blue markings); complexly patterned (spotted and mostly interruptedly banded with blue in both sexes, with a medianly broadened uninterrupted blue band on segment 2 in the male); without a yellow triangle on segment 2; with mid-dorsal spots. Abdominal segments 9 and 10 unbanded, but each with a pair of more or less rectangular 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, 30–40 mm long (“about 35 mm”).

The eyes large; approaching one another closely at a point on the top of the head; convex dorsally, their posterior margins not aligned. 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 7 segmented. The mask shortly abruptly narrowed well before the hinge, with the prementum stalked to narrowed gradually to the hinge (the prementum relatively elongated). The prementum quite elongated, being nearly twice as long as the width of its front. The mask with a flat prementum; with a short slit-like median cleft. The prementum bearing 0 major setae. The body of the labial palps bearing 0 major setae. Distal margins of the labial palps entire. 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 Scotland and southern Scotland (mostly in the north, and nowhere common). Adults on the wing late may to early August (generally in best mature condition mid-June to late July).

Classification. Anisoptera; family Aeshnidae.

Illustrations. • Aeshna caerulea (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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