British Insects: the Odonata
Scarce Chaser Dragonfly.
Adults. Adults about 41–44–48 mm long (the sexes similar in length). Average wingspan 74 mm; hindwings 35–38 mm long.
The eyes dorsally narrowly apposed to dorsally broadly contiguous; blue.
Legs black and brown (the femora brown). 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 (the forewings of the male), or suffused with colour basally and in the leading half (the forewings of the female), or with a sharply defined, dark brown basal fascia (the hindwings only, in both sexes). The tinting 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 11–14 (fewer in the hindwings). Pterostigma well over twice but no more than five times as long as wide; black.
Abdomen broadly lanceolate; 26–29 mm long; predominantly blue (pruinescent sky blue in segments 1 to 7 of the mature male), or yellow to brown (yellowish or light brown in females and immature males, the former with conspicuous median black markings on segments 3–10); plain (but darkened over segments 8 to 10 in the mature male), or predominantly longitudinally lined (that of the female with conspicuously medianly black-banded over segments 3 to 10); 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, 22–25 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 three long setae near each lateral margin, with slightly anterior to them a chain of two to five short spiniform setae extending forwards to two medial fields of about ten short spiniform setae: i.e., the setae arranged in six distinct fields. The body of the labial palps bearing 4(–5) 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 9. The abdomen with a prominent mid-dorsal spine on segment 8; gizzard with 4–8 folds.
Distribution. English Midlands, East Anglia, southeast England, southwest England, and central southern England. Adults on the wing early May to late July (generally in best mature condition early to late June).
Classification. Anisoptera; family Libellulidae.
Illustrations. • Libellula fulva (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’.