British Insects: Odonata (Dragonflies and Damselflies)

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L. Watson and M. J. Dallwitz

Conventional key

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1(0).
  • Thoracic antehumeral stripes present ... 2
  • Thoracic antehumeral stripes absent... 31

2(1).
  • The eyes lateral and widely separated ... 3
  • The eyes dorsally narrowly apposed... 17
  • The eyes dorsally broadly contiguous... 23

3(2).
  • Average wingspan up to 40 mm ... 4
  • Average wingspan 40 to 60 mm... 10
  • Average wingspan 60 to 80 mm... Gomphus vulgatissimus

4(3).
  • The hindwings with only one row of cells distal to the pterostigma between the costa and the radial vein ... 5
  • The hindwings with two rows of cells distal to the pterostigma between the costa and the radial vein... Enallagma cyathigerum

5(4).
  • Legs pale red; the head of nymphs in dorsal view not markedly narrowing from immediately behind the eyes ... Ceriagrion tenellum
  • Legs not red; the head of nymphs in dorsal view markedly narrowing from immediately behind the eyes... 6

6(5).
  • The front of the head immediately interior to the eyes pale whitish blue; the caudal lamellae of nymphs oval (broadest in the middle, symmetrically curved) ... 7
  • The front of the head immediately interior to the eyes not pale whitish blue; the caudal lamellae of nymphs oblanceolate or obovate: broader and more strongly curved beyond the middle... 9

7(6).
  • Abdominal segment 8 of the female with a ventral apical spine; the outer margins of the labial palps of nymphs without spines; the caudal lamellae of nymphs with one margin hairless beyond the middle, the other hairy to nearer the apex ... 8
  • Abdominal segment 8 of the female without a ventral apical spine; the outer margins of the labial palps of nymphs armed with small spines; the caudal lamellae of nymphs hairy on both margins to beyond the middle... Coenagrion mercuriale

8(7).
  • Pterostigma more or less isodiametric ... Ischnura pumilio
  • Pterostigma elongated but only about about twice as long as wide... Ischnura elegans
  • Pterostigma well over twice but no more than five times as long as wide... Ischnura elegans

9(6).
  • northern Scotland; pterostigma more or less isodiametric; the caudal lamellae of nymphs hyaline without coloured markings; the caudal lamellae of nymphs hairy on both margins to beyond the middle; the head of nymphs with prominent spots ... Coenagrion hastulatum
  • southeast England; pterostigma elongated but only about about twice as long as wide; the caudal lamellae of nymphs with transverse dark bands; the caudal lamellae of nymphs with one margin hairless beyond the middle, the other hairy to nearer the apex; the head of nymphs without prominent spots... Coenagrion scitulum

10(3).
  • Hind tibia of adults with a conspicuous featherlike expansion; the antennae of nymphs with the first flagellar segment shorter than the pedicel; the outer margins of the labial palps of nymphs armed with small spines ... Platycnemis pennipes
  • Hind tibia of adults without a featherlike expansion; the antennae of nymphs with the first flagellar segment longer than the pedicel; the outer margins of the labial palps of nymphs without spines... 11

11(10).
  • Thoracic antehumeral stripes greyish ... 12
  • Thoracic antehumeral stripes blue... 13
  • Thoracic antehumeral stripes green... 15
  • Thoracic antehumeral stripes yellow... Pyrrhosoma nymphula
  • Thoracic antehumeral stripes orange... Pyrrhosoma nymphula
  • Thoracic antehumeral stripes red... 16
  • Thoracic antehumeral stripes brown... Erythromma najas

12(11).
  • The prothorax deeply two-cleft posteriorly, resulting in a distinctly 3-lobed posterior margin; the caudal lamellae of nymphs blunt ... Coenagrion pulchellum
  • The prothorax posteriorly more or less entire; the caudal lamellae of nymphs pointed... Coenagrion puella

13(11).
  • The prothorax deeply two-cleft posteriorly, resulting in a distinctly 3-lobed posterior margin; the caudal lamellae of nymphs blunt ... Coenagrion pulchellum
  • The prothorax posteriorly more or less entire; the caudal lamellae of nymphs pointed... 14

14(13).
  • Abdominal segment 2 of the male blue, with a black U-shaped dorsal mark which is separated from the black circlet behind it ... Coenagrion puella
  • Abdominal segment 2 of the male blue, with a black U-shaped dorsal mark which is joined to the black circlet behind it... Coenagrion puella
  • Abdominal segment 2 of the male blue, with a more or less spear-shaped but variable dorsal black mark joined to the black posterior circlet, and consistently exhibiting a black line on either side... Coenagrion hastulatum

15(11).
  • northern Scotland; abdominal segment 2 of the male blue, with a more or less spear-shaped but variable dorsal black mark joined to the black posterior circlet, and consistently exhibiting a black line on either side ... Coenagrion hastulatum
  • East Anglia; abdominal segment 2 of the male blue, with only a broad black band near the middle... Coenagrion armatum

16(11).
  • The hindwings with only one row of cells distal to the pterostigma between the costa and the radial vein; abdomen more or less linear from base to tip; pterostigma pale with a dark centre; the caudal lamellae of nymphs pointed; the caudal lamellae of nymphs patterned beyond the middle with conspicuous a dark cross ... Pyrrhosoma nymphula
  • The hindwings with two rows of cells distal to the pterostigma between the costa and the radial vein; abdomen more or less linear from a conspicuously swollen base; pterostigma light brown; the caudal lamellae of nymphs blunt; the caudal lamellae of nymphs with transverse dark bands... Erythromma najas

17(2).
  • Thoracic antehumeral stripes blue ... Aeshna caerulea
  • Thoracic antehumeral stripes green... Libellula depressa
  • Thoracic antehumeral stripes yellow... 18
  • Thoracic antehumeral stripes red... Leucorrhinia dubia
  • Thoracic antehumeral stripes brown... 19

18(17).
  • Average wingspan 40 to 60 mm ... Leucorrhinia dubia
  • Average wingspan 60 to 80 mm... Libellula depressa
  • Average wingspan 80 mm or more... Cordulegaster boltonii

19(17).
  • The narrow black band at the base of the frons conspicuously continued for some distance down the inner sides of the eyes ... 20
  • The narrow black band at the base of the frons only briefly continued down the inner sides of the eyes... 21
  • The narrow black band at the base of the frons not continued down the inner sides of the eyes... 22

20(19).
  • Pterostigma reddish brown ... Sympetrum vulgatum
  • Pterostigma orange... Orthetrum coerulescens
  • Pterostigma red... Sympetrum vulgatum

21(19).
  • Antenodal veins in the forewings 6 to 8 ... Sympetrum nigrescens
  • Antenodal veins in the forewings 9 to 10... Orthetrum coerulescens
  • Antenodal veins in the forewings 11 to 18... Orthetrum coerulescens

22(19).
  • Pterostigma reddish brown ... Sympetrum striolatum
  • Pterostigma orange... Orthetrum coerulescens
  • Pterostigma red... Sympetrum striolatum

23(2).
  • Thoracic antehumeral stripes blue ... Aeshna caerulea
  • Thoracic antehumeral stripes green... 24
  • Thoracic antehumeral stripes yellow... 26
  • Thoracic antehumeral stripes brown... 27

24(23).
  • Average wingspan 60 to 80 mm; abdomen without a yellow triangle on segment 2; antenodal veins in the forewings 11 to 18; the eyes of nymphs lateral and widely separated on the top of the head ... 25
  • Average wingspan 80 mm or more; abdomen with a conspicuous, median yellow triangle on segment 2; antenodal veins in the forewings 19 to 30; the eyes of nymphs approaching one another closely at a point on the top of the head... Aeshna cyanea

25(24).
  • Pterostigma well over twice but no more than five times as long as wide; the male abdomen without auricles on segment 2; legs black and brown; adults (front of head to tip of abdomen, including anal appendages) 30 to 50 mm long; thorax not very hairy ... Libellula depressa
  • Pterostigma narrow-linear; the male abdomen auriculate on segment 2; legs black; adults (front of head to tip of abdomen, including anal appendages) 50 to 80 mm long; thorax very hairy... Brachytron pratense

26(23).
  • Average wingspan 60 to 80 mm; the forewings and hindwings with a sharply defined, dark brown basal fascia; abdomen lanceolate (relatively broad, dorsiventrally flattened); the male abdomen without auricles on segment 2; adults (front of head to tip of abdomen, including anal appendages) 30 to 50 mm long ... Libellula depressa
  • Average wingspan 80 mm or more; the forewings and hindwings unpatterned and clear; abdomen more or less linear from a conspicuously swollen base; the male abdomen auriculate on segment 2; adults (front of head to tip of abdomen, including anal appendages) 50 to 80 mm long... Aeshna juncea

27(23).
  • The narrow black band at the base of the frons conspicuously continued for some distance down the inner sides of the eyes ... 28
  • The narrow black band at the base of the frons only briefly continued down the inner sides of the eyes... 29
  • The narrow black band at the base of the frons not continued down the inner sides of the eyes... 30

28(27).
  • Pterostigma reddish brown ... Sympetrum vulgatum
  • Pterostigma orange... Orthetrum coerulescens
  • Pterostigma red... Sympetrum vulgatum

29(27).
  • Antenodal veins in the forewings 6 to 8 ... Sympetrum nigrescens
  • Antenodal veins in the forewings 9 to 10... Orthetrum coerulescens
  • Antenodal veins in the forewings 11 to 18... Orthetrum coerulescens

30(27).
  • Pterostigma reddish brown ... Sympetrum striolatum
  • Pterostigma orange... Orthetrum coerulescens
  • Pterostigma red... Sympetrum striolatum

31(1).
  • Average wingspan up to 40 mm ... 32
  • Average wingspan 40 to 60 mm... 34
  • Average wingspan 60 to 80 mm... 42
  • Average wingspan 80 mm or more... 56

32(31).
  • Legs pale red; the front of the head immediately interior to the eyes not pale whitish blue; abdominal segment 8 of the female without a ventral apical spine; the head of nymphs in dorsal view not markedly narrowing from immediately behind the eyes; the caudal lamellae of nymphs oblanceolate or obovate: broader and more strongly curved beyond the middle ... Ceriagrion tenellum
  • Legs not red; the front of the head immediately interior to the eyes pale whitish blue; abdominal segment 8 of the female with a ventral apical spine; the head of nymphs in dorsal view markedly narrowing from immediately behind the eyes; the caudal lamellae of nymphs oval (broadest in the middle, symmetrically curved)... 33

33(32).
  • Pterostigma more or less isodiametric ... Ischnura pumilio
  • Pterostigma elongated but only about about twice as long as wide... Ischnura elegans
  • Pterostigma well over twice but no more than five times as long as wide... Ischnura elegans

34(31).
  • The wings held vertically in repose ... 35
  • The wings spread more or less horizontally in repose... 37
  • The wings held partly open in repose... 41

35(34).
  • The forewings and hindwings petiolate (basally narrowed); abdomen predominantly transversely banded; abdomen non-metallic; antenodal veins in the forewings 2; the antennae of nymphs with the scape considerably shorter than the other segments taken together ... 36
  • The forewings and hindwings sessile; abdomen plain; abdomen metallic; antenodal veins in the forewings 19 to 30; the antennae of nymphs with the scape as long as the other segments taken together... Agrion virgo

36(35).
  • The hindwings with only one row of cells distal to the pterostigma between the costa and the radial vein; pterostigma more or less isodiametric; abdomen more or less linear from base to tip; the caudal lamellae of nymphs pointed; the caudal lamellae of nymphs hyaline without coloured markings ... Coenagrion armatum
  • The hindwings with two rows of cells distal to the pterostigma between the costa and the radial vein; pterostigma elongated but only about about twice as long as wide; abdomen more or less linear from a conspicuously swollen base; the caudal lamellae of nymphs blunt; the caudal lamellae of nymphs with transverse dark bands... Erythromma najas

37(34).
  • The inner wing venation red ... Sympetrum fonscolombei
  • The inner wing venation brown... 38
  • The inner wing venation blackish... 39

38(37).
  • The narrow black band at the base of the frons conspicuously continued for some distance down the inner sides of the eyes ... Sympetrum vulgatum
  • The narrow black band at the base of the frons only briefly continued down the inner sides of the eyes... Sympetrum nigrescens
  • The narrow black band at the base of the frons not continued down the inner sides of the eyes... Sympetrum striolatum

39(37).
  • Legs black ... 40
  • Legs black and yellow... Sympetrum flaveolum

40(39).
  • Pterostigma black ... Sympetrum scoticum
  • Pterostigma reddish brown... Sympetrum sanguineum
  • Pterostigma red... Sympetrum sanguineum

41(34).
  • Pterostigma elongated but only about about twice as long as wide; the moveable hooks of the labial palps of nymphs with three or more setae ... Lestes dryas
  • Pterostigma well over twice but no more than five times as long as wide; the moveable hooks of the labial palps of nymphs with two setae... Lestes sponsa

42(31).
  • The wings held vertically in repose; the male abdomen with paired inferior anal appendages; the forewings and hindwings similar in shape and venation; discoidal cell of forewings and hindwings a simple quadrilateral, not longitudinally divided; the nymphs elongate and slender-bodied, gradually tapering posteriorly ... 43
  • The wings spread more or less horizontally in repose; the male abdomen with a single inferior anal appendage; the forewings and hindwings dissimilar in shape and venation (the hindwings broadened basally); discoidal cell of forewings and hindwings divided longitudinally into a conspicuous triangle and supra-triangle; the nymphs stout, the body expanded in the middle... 44

43(42).
  • The cleft in the prementum of the nymphs less than four times as long as its maximum width ... Agrion splendens
  • The cleft in the prementum of the nymphs more than four time as long as its maximum width... Agrion virgo

44(42).
  • The male abdomen auriculate on segment 2 ... 45
  • The male abdomen without auricles on segment 2... 53

45(44).
  • The eyes dorsally narrowly apposed ... 46
  • The eyes dorsally broadly contiguous... 49

46(45).
  • Abdomen plain ... 47
  • Abdomen predominantly longitudinally lined... Oxygastra curtisii
  • Abdomen complexly patterned... Aeshna caerulea

47(46).
  • The wings tinted amber; pterostigma dark brown ... 48
  • The wings tinted light brown; pterostigma black... Cordulia linaenea

48(47).
  • Abdomen metallic; the abdomen of nymphs with mid-dorsal spines ... Somatochlora metallica
  • Abdomen non-metallic; the abdomen of nymphs without mid-dorsal spines... Somatochlora arctica

49(45).
  • Abdomen plain ... 50
  • Abdomen predominantly longitudinally lined... 51
  • Abdomen complexly patterned... 52

50(49).
  • Abdomen metallic; the abdomen of nymphs with mid-dorsal spines ... Somatochlora metallica
  • Abdomen non-metallic; the abdomen of nymphs without mid-dorsal spines... Somatochlora arctica

51(49).
  • Pterostigma well over twice but no more than five times as long as wide; abdomen metallic; antenodal veins in the forewings without distinct primaries, and those in the costal and subcostal spaces more or less aligned; abdomen without mid-dorsal spots; thorax not very hairy ... Oxygastra curtisii
  • Pterostigma narrow-linear; abdomen non-metallic; antenodal veins in the forewings incorporating two conspicuously stronger primaries, and those in the costal and subcostal spaces unaligned; abdomen with mid-dorsal spots; thorax very hairy... Brachytron pratense

52(49).
  • Pterostigma well over twice but no more than five times as long as wide; abdomen predominantly brown; thorax not very hairy; the eyes of nymphs approaching one another closely at a point on the top of the head; the head of nymphs in dorsal view not markedly narrowing from immediately behind the eyes ... Aeshna caerulea
  • Pterostigma narrow-linear; abdomen predominantly black; thorax very hairy; the eyes of nymphs lateral and widely separated on the top of the head; the head of nymphs in dorsal view markedly narrowing from immediately behind the eyes... Brachytron pratense

53(44).
  • The inner wing venation red ... Sympetrum fonscolombei
  • The inner wing venation brown... Sympetrum vulgatum
  • The inner wing venation blackish... 54

54(53).
  • Legs black ... Libellula quadrimaculata
  • Legs black and brown... 55

55(54).
  • The forewings and hindwings unpatterned and clear ... Orthetrum cancellatum
  • The forewings and hindwings suffused with colour at their bases only... Libellula fulva
  • The forewings and hindwings suffused with colour basally and in the leading half... Libellula fulva
  • The forewings and hindwings with a sharply defined, dark brown basal fascia... Libellula fulva

56(31).
  • Abdomen plain ... Aeshna isosceles
  • Abdomen predominantly longitudinally lined... Anax imperator
  • Abdomen complexly patterned... 57

57(56).
  • Abdominal segments 9 and 10 unbanded, but each with a pair of rounded posterior spots ... 58
  • Abdominal segments 9 and 10 unbanded, but each with a pair of more or less rectangular spots... Aeshna caerulea
  • Abdominal segments 9 and 10 neither colour-banded nor colour-spotted... Aeshna grandis

58(57).
  • Abdomen 35 to 49 mm long; antenodal veins in the forewings 11 to 18; the prementum of nymphs quite elongated, being nearly twice as long as the width of its front ... Aeshna mixta
  • Abdomen 50 mm long or more; antenodal veins in the forewings 19 to 30; the prementum of nymphs relatively short, being much less than twice as long as its front width... Aeshna juncea

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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