British Insects: the Odonata
Four-spotted Chaser Dragonfly.
Adults. Adults about 39–43–47 mm long (the sexes similar in length). Average wingspan 75 mm; hindwings 32–40 mm long.
The eyes dorsally narrowly apposed to dorsally broadly contiguous; brown.
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 forewings of both sexes), or with a sharply defined, dark brown basal fascia. The tinting of the forewing bases amber to light brown. The inner wing venation blackish. Discoidal cell divided longitudinally into a conspicuous triangle and supra-triangle. Antenodal veins in the forewings 15–17 (fewer in the hindwings). Pterostigma well over twice but no more than five times as long as wide; black.
Abdomen broadly lanceolate; 27–32 mm long; predominantly brown (in both sexes, usually with yellow lateral markings); predominantly longitudinally lined (laterally: with a large, conspicuous, yellow lateral longitudinal band on either side of each of the middle abdominal segments); without mid-dorsal spots. The male abdomen without auricles on segment 2; with a single inferior anal appendage.
Nymphs. The nymphs stout, the body expanded in the middle; when mature, 22–26 mm long.
The postocular lobes curving sharply to the back of the head from some distance behind the eyes. The antennae 7 segmented. The mask narrowed gradually to the hinge; having the prementum hollowed dorsally; without a median cleft. The prementum bearing 16–26 major setae (8+8 to 13+13, in alignment). The body of the labial palps bearing 7–8(–11) major setae. Distal margins of the labial palps weakly crenate. Legs longer than the abdomen.
The abdomen terminating in five short spine-like appendages. The cerci no more than hald the length of the paraprocts. The abdomen with mid-dorsal spines. The mid-dorsal abdominal spines prominent on segments 4 to 8. The abdomen with a prominent mid-dorsal spine on segment 8; gizzard with 4–8 folds.
Distribution. Northern Scotland, southern Scotland, northern England, English Midlands, East Anglia, Wales, southeast England, southwest England, Isle of Wight, Ireland, and central southern England. Adults on the wing late April to early September (generally in best mature condition late May to early August).
Classification. Anisoptera; family Libellulidae.
General comments. Both sexes exhibiting a characteristic dark spot, varying in geographically compactness, at the nodus of each wing.
Illustrations. • Libellula quadrimaculata (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’.