Dennis Paulson
Introduction and names revised January 2007
This key has been prepared to provide identification in life of adults of the species of Odonata that occur in Washington. Coloration is given much weight in the key, which would not be possible with dried specimens. Wing venation, the basis of many dragonfly keys, is ignored, although other structural attributes of the species are used when necessary. A 10x hand lens or magnifying glass is essential to see some of these characteristics, although a pair of binoculars can be just as effective if you reverse them. A small millimeter ruler is also necessary, as some species are distinguished by size.
An insect net is another essential, as the species will have to be learned by keying them out in the hand. Many details, although clearly visible at close range, cannot be seen at a distance, and they must be noted to proceed through the key. Once the species are learned in the hand, many of them will be easily recognizable in the field.
Each number in the key contains a pair of statements, each of which describes distinguishing characteristics. Read each statement before deciding to accept or reject either one, and note that some of them list more than one characteristic. Each one will lead either to a species name or another number. Measurements listed refer to total length unless otherwise indicated. When two are more species are listed together, they are difficult to distinguish in the field but differ by structural characteristics that are explained and illustrated in more technical books such as Introduction to the Dragonflies of British Columbia and Yukon, by Robert Cannings, The Odonata of Canada and Alaska, by Edmund Walker, Dragonflies of North America, by James Needham, Minter Westfall, and Michael May, and Damselflies of North America, by Minter Westfall and Michael May.
Males and females can be distinguished as follows. Males have a bump containing the accessory genitalia under the second abdominal segment; females lack this. Females typically have a broader abdomen than males, and female damselflies, petaltails, and darners have a prominent ovipositor under the last segment. Male dragonflies have 3 appendages at the abdomen tip, male damselflies 4; females of both have only 2 such appendages, usually smaller and often inconspicuous. Some key couplets refer to only one sex.
The key works for some teneral (just emerged) individuals, but at this age, color patterns are often insufficiently developed to be diagnostic. The definitive coloration of adults is acquired slowly with maturation, and individuals that are not yet mature may not be fully colored. Male dragonflies on territory at the water or individuals of either sex engaged in reproductive behavior will surely be mature. Some adults become pruinose, with a blue or whitish powdery bloom that covers parts of the body.
Familiarize yourself with basic dragonfly anatomy: head, thorax and abdomen, the latter with 10 segments. Anterior=front, posterior=rear, lateral=side, dorsal=top, ventral=bottom. Note the rectangular pterostigma near the tip of each wing.
Species added to the state list since the construction of this key, all of them localized and rare, include Coenagrion interrogatum (Subarctic Bluet), Aeshna subarctica (Subarctic Darner), Somatochlora franklini (Delicate Emerald), and Somatochlora whitehousei (Whitehouse's Emerald).
First key the dragonfly in the Key to Families, then go to the appropriate family and key it to species.
Key to Families
- Head widened so eyes farther apart than their own diameter; wings held together over abdomen (mostly open but not flat in one family); slender-bodied and mostly small..........Zygoptera (damsels)..........2
Eyes closer together than their own diameter (touching in most species); wings held wide open, flat; heavier-bodied and mostly large..........Anisoptera (dragons)..........4 - Wings with wide black tips; large (>=45mm)..........Calopterygidae
Wings clear (except for small, rectangular pterostigma near the end); smaller (<40 mm except for one large species)..........3 - Pterostigma long, equal to eye diameter; wings held open (closed in hand, may be closed in tenerals); ..........Lestidae
Length of pterostigma less than diameter of eye; wings closed over abdomen (partially open in some individuals or in hand); ..........Coenagrionidae - Eyes completely separated..........5
Eyes just touching or broadly contiguous..........6 - Thorax black with numerous yellow spots..........Petaluridae
Thorax colored otherwise..........Gomphidae - Large (>70mm); eyes barely touching; black with two yellow stripes on thorax and yellow spots on abdomen..........Cordulegastridae
Not that combination of characters; if large and with pale stripes on thorax, then eyes broadly contiguous..........7 - Larger (>55mm); abdomen spotted or otherwise marked with paler color..........8
Smaller (<55 mm), abdomen entirely black in species longer than 50 mm..........9 - Each abdominal segment with a single central yellow spot; conspicuous single stripe on each side of thorax..........Macromiidae
Each abdominal segment with multiple spots or none; thorax with two side stripes or none..........Aeshnidae - Abdomen almost entirely black and eyes bright green or turquoise..........Corduliidae
Abdomen variously colored; if entirely black, then eyes not green; if eyes green, then body not black..........10 - Anal loop of hind wing short and rounded (see illustration)..........Corduliidae
Anal loop of hind wing longer and pointed at tip..........Libellulidae
Corduliidae anal loop |
Libellulidae anal loop |
Calopterygidae (jewelwings)
One species..........Calopteryx aequabilis (River Jewelwing)
Lestidae (spreadwings)
- Larger (>45mm); contrasty white stripe on side of thorax..........Archilestes californicus (California Spreadwing)
Smaller (<45mm); no white stripe on side of thorax..........2 - Thorax metallic green above, without longitudinal stripes..........Lestes dryas (Emerald Spreadwing)
Thorax bronzy to black above, if green with a pale longitudinal stripe on either side..........3 - Thorax with at least 4 prominent dark spots below; male inferior appendages 50% length of superiors..........Lestes congener (Spotted Spreadwing)
Thorax with no ventral markings or inconspicuous spot on either side; male inferior appendages 80% length of superiors..........4 - Rear of head partly pale, pterostigma light to medium brown, pale at ends; male superior appendages pale at base; from below, male inferior appendages curved outward toward tips..........Lestes unguiculatus (Lyre-tipped Spreadwing)
Rear of head entirely dark, pterostigma usually uniformly dark; from below, male inferior appendages straight throughout..........Lestes disjunctus (Northern Spreadwing)
Coenagrionidae (pond damsels)
- Red with top of thorax and tip of abdomen black (male) or reddish to brown with no pattern (female)..........Amphiagrion abbreviatum (Western Red Damsel)
Not red or reddish, if so thorax with at least a middorsal black stripe..........2 - Abdomen black with blue tip..........3
Abdomen mostly black (segment 8 may be pale) or patterned alternately blue and black or brown and black..........7 - Top of thorax entirely metallic green..........Nehalennia irene (Sedge Sprite)
Top of thorax with stripes or dots..........4 - Top of thorax dark with 4 isolated pale dots..........Ischnura cervula (Pacific Forktail)
Top of thorax with dark and pale stripes or entirely dull..........5 - Only segment 8 blue above..........Ischnura cervula (Pacific Forktail)
Segments 8 & 9 blue above..........6 - Thorax green on sides; smaller (<=25mm)..........Ischnura perparva (Western Forktail)
Thorax blue on sides; larger (>30mm)..........Ischnura erratica (Swift Forktail) - Males (mostly blue or violet, genitalia visible under 2nd abdominal segment, 4 appendages at tip of abdomen)..........8
Females (mostly brown, gray and/or black but may be almost as blue as males, no genitalia on 2nd abdominal segment, 2 appendages and ovipositor at tip of abdomen)..........15 - Pale color mostly violet (immatures bluish); black line on top of thorax very narrow..........Argia emma (Emma's Dancer)
Pale color mostly blue; top of thorax with conspicuous black stripe..........9 - Dark side stripe on upper part of thorax seems to end at midlength (fine line beyond it)..........Argia vivida (Vivid Dancer)
Dark side stripe on thorax same width throughout..........10 - Middle abdominal segments mostly blue from above..........11
Middle abdominal segments at least 50% black from above..........12 - Superior and inferior appendages about same length..........Enallagma ebrium (Marsh Bluet)
Inferior appendages longer, projecting well beyond superiors..........Enallagma boreale (Boreal Bluet), E. annexum (Northern Bluet) - Black marking on second abdominal segment U-shaped; thorax green tinged..........Coenagrion resolutum (Taiga Bluet)
Black spot on rear of second abdominal segment; thorax entirely blue..........13 - Third abdominal segment <50% blue..........Enallagma carunculatum (Tule Bluet)
Third abdominal segment >50% blue..........14 - At alkaline lakes of Columbia Basin..........Enallagma clausum (Alkali Bluet)
Elsewhere..........some Enallagma cyathigerum (Northern Bluet) - Abdomen mostly light brown or blue above..........16
Abdomen mostly or all black or pruinose gray above..........17 - Black middorsal stripe on thorax no wider than lateral stripes..........Argia emma (Emma's Dancer)
Black middorsal stripe on thorax much wider than lateral stripes..........Argia vivida (Vivid Dancer) - Pruinose light gray..........Ischnura perparva (Western Forktail)
No pruinosity..........18 - Ground color of thorax orange to pinkish..........19
Ground color of thorax blue to greenish or brown to tan..........21 - Orange on base of abdomen extending to segment 3..........Ischnura perparva (Western Forktail)
Orange on base of abdomen limited to segment 1 or 1-2..........20 - Segment 8 of abdomen black above..........Ischnura erratica (Swift Forktail)
Segment 8 of abdomen pale above..........Ischnura cervula (Pacific Forktail) - Middle abdominal segments (4-6) entirely black above (or pale color of sides extends upward at anterior edge of segment but only narrowly and not to midline)..........22
Light color of sides clearly extending as a wedge, usually to midline, at front of each middle abdominal segment..........27 - Extensive pale color on top of segment 8 or 9..........23
Segment 8 and 9 of abdomen entirely black above (may be narrow pale ring at rear)..........24 - Thorax entirely dark, or if pattern can be seen, then dark stripe on side narrower than pale stripe above it..........Ischnura cervula (Pacific Forktail)
Thorax distinctly striped, dark stripe on side about same width as pale stripe above it..........Ischnura erratica (Swift Forktail) - Thorax entirely dark, or if pattern can be seen, then dark stripe on side narrower than pale stripe above it..........Ischnura cervula (Pacific Forktail)
Thorax distinctly striped, dark stripe on side about same width as pale stripe above it..........25 - Larger (>=33 mm)..........Ischnura erratica (Swift Forktail)
Smaller (<33 mm)..........26 - Segments 7 and 8 of abdomen with conspicuous pale ring at end..........Coenagrion resolutum (Taiga Bluet)
Segments 7 and 8 of abdomen entirely black above..........Enallagma ebrium (Marsh Bluet) - Segment 8 of abdomen entirely black above..........Enallagma carunculatum (Tule Bluet), E. ebrium (Marsh Bluet)
Segment 8 of abdomen entirely or partially pale above..........Enallagma boreale (Boreal Bluet), E. clausum (Alkali Bluet), E. annexum (Northern Bluet)
Petaluridae (petaltails)
One species..........Tanypteryx hageni (Black Petaltail)
Gomphidae (clubtails)
- Abdomen almost entirely black..........Octogomphus specularis (Grappletail)
Abdomen with conspicuous pale markings..........2 - Thorax distinctly green; male inferior appendages pointed..........3
Thorax gray to yellow, or greenish; male inferior appendages forked..........5 - Sides of thorax heavily striped with black, whitish between one pair of stripes..........Erpetogomphus compositus (White-belted Ringtail)
Sides of thorax entirely green..........4 - A pair of fine dark lines, almost touching, where front and sides of thorax meet..........Ophiogomphus occidentis (Sinuous Snaketail)
A fine dark line and an oval spot in front of it in same area, or no markings..........Ophiogomphus severus (Pale Snaketail) - Sides of thorax without conspicuous stripes behind front edge of fore wing..........Stylurus olivaceus (Olive Clubtail)
Sides of thorax with narrow to broad conspicuous stripes below wing bases..........6 - Conspicuous stripe on side of thorax behind wing bases..........Gomphus lynnae (Columbia Clubtail)
No stripe on side of thorax behind hind wing base..........7 - Dark stripe on side of thorax as wide as one in front of it..........Gomphus graslinellus (Pronghorn Clubtail)
Dark stripe on side of thorax much narrower than one in front of it..........Gomphus kurilis (Pacific Clubtail)
Aeshnidae (darners)
- Thorax entirely green..........Anax junius (Common Green Darner)
Thorax dark with pale stripes on sides..........2 - Males (3 terminal appendages on abdomen)..........3
Females (2 terminal appendages and ovipositor on abdomen..........13 - Superior appendages forked at tip in side view; eyes, face, and thoracic stripes bright blue..........Rhionaeschna multicolor (Blue-eyed Darner)
Superior appendages simple or paddle-shaped; eyes, face, and thoracic stripes not all bright blue..........4 - Small for family (<=65mm)..........5
Normal sized for family (>65mm)..........6 - Anterior lateral thoracic stripe bent twice in middle..........Aeshna sitchensis (Zigzag Darner)
Anterior lateral thoracic stripe straight..........Rhionaeschna californica (California Darner) - Superior appendages paddle-shaped in side view, expanded toward tip with conspicuous spine there..........7
Superior appendages simple, more or less pointed at tip..........9 - Abdominal spots small, 15-20% length of each segment, lacking on 10th segment; paired blue spots on underside of abdomen..........Aeshna umbrosa (Shadow Darner)
Abdominal spots larger, 25-33% length of each segment, conspicuous on 10th segment; no blue spots on underside of abdomen..........8 - Narrow black line across face; lateral thoracic stripes rather straight and parallel-sided..........Aeshna palmata (Paddle-tailed Darner)
No black line on face; lateral thoracic stripes indented in middle and with projection to rear at upper end..........Aeshna constricta (Lance-tipped Darner) - Segment 10 of abdomen black; lateral thoracic stripes broad and straight in front; superior appendages with tubercle under base..........Aeshna tuberculifera (Black-tipped Darner)
Segment 10 of abdomen largely blue; lateral thoracic stripes interrupted or angled (if straight, then either quite narrow or with fine stripe between them); no tubercle under superior appendage..........10 - Stripes on front of thorax reduced to fine streaks at midheight; lateral stripes of thorax narrow and straight or reduced to pairs of dots..........Aeshna interrupta (Variable Darner)
Stripes on front of thorax broader, extending to upper edge, or represented there by isolated dots; lateral stripes well developed..........11 - At least one of lateral thoracic stripes indented in middle..........12
Lateral thoracic stripes straight..........Aeshna juncea (Sedge Darner) - Narrow black line across face; no distinct blue spots under abdomen..........Aeshna eremita (Lake Darner)
No black line on face; middle abdominal segments with blue spots beneath..........Aeshna canadensis (Canada Darner) - Small for family (<=65mm)..........14
Normal sized for family (>65mm)..........15 - Small but obvious tubercle (bump) under first abdominal segment; anterior lateral thoracic stripe straight..........Rhionaeschna californica (California Darner)
No tubercle under first abdominal segment; anterior lateral thoracic stripe bent twice in middle..........Aeshna sitchensis (Zigzag Darner) - Small but obvious tubercle (bump) under first abdominal segment..........Rhionaeschna multicolor (Blue-eyed Darner)
No tubercle under first abdominal segment..........16 - Styli (hairlike projections) of ovipositor as long as 10th abdominal segment; terminal appendages wide (>=2mm)..........17
Styli much shorter than 10th abdominal segment; terminal appendages narrow (1.5mm), may be missing..........18 - Lateral thoracic stripes same shape, straight and with blackish borders..........Aeshna tuberculifera (Black-tipped Darner)
Anterior lateral thoracic stripe indented in middle and usually extended as a hook at upper end, no blackish borders..........Aeshna constricta (Lance-tipped Darner) - Underside of most abdominal segments with light basal spot on each side..........19
Underside of abdomen entirely dark..........21 - Anterior lateral thoracic stripe indented in middle and usually extended as a hook at upper end..........Aeshna canadensis (Canada Darner)
Lateral thoracic stripes both straight..........20 - Narrow light stripe between relatively broad thoracic stripes; usually narrow light stripes on front of thorax..........Aeshna juncea (Sedge Darner)
No stripe between relatively narrow thoracic stripes; front of thorax unmarked..........Aeshna umbrosa (Shadow Darner) - Thoracic stripes relatively broad, anterior one conspicuously indented at midlength..........22
Thoracic stripes relatively narrow and straight, may be slightly sinuous, or each represented by a pair of spots..........23 - Narrow black line across face; larger (>64 mm)..........Aeshna eremita (Lake Darner)
Face unmarked; smaller (<62mm)..........Aeshna canadensis (Canada Darner) - Valves of ovipositor in side view very slightly sinuous--broadest at middle, then slightly narrowed, then slightly expanded at tip; difference seen only with adequate magnification..........Aeshna palmata (Paddle-tailed Darner)
Valves of ovipositor straight in side view..........Aeshna interrupta (Variable Darner)
Cordulegastridae (spiketails)
One species..........Cordulegaster dorsalis (Pacific Spiketail)
Macromiidae (river cruisers)
One species..........Macromia magnifica (Western River Cruiser)
Corduliidae (emeralds)
- Abdomen with yellowish sides; thorax brown with pale hairs..........2
Abdomen entirely black; thorax largely or partly metallic dark green, with or without yellow spots..........3 - Face from above mostly pale; male superior appendages sharply angled near end; female appendages about 2mm long..........Epitheca canis (Beaverpond Baskettail)
Face from above mostly dark; male superior appendages not angled; female appendages about 3mm long..........Epitheca spinigera (Spiny Baskettail) - A very fine white ring at base of each abdominal segment..........Somatochlora albicincta (Ringed Emerald)
No white rings on middle abdominal segments (may be white ring on basal segment and/or yellow dots on side of each segment)..........4 - Thorax with no indication of yellow on sides; male inferior appendage forked; female appendages <=2mm long..........Cordulia shurtleffii (American Emerald)
Thorax with one or more yellow spots on sides (may be faint, check other characters); male inferior appendage pointed; female appendages >=3mm..........5 - Larger (>=50mm); male superior appendages approaching at tip in a smooth curve; female with vulvar lamina smaller, shorter than abdominal segment 9..........Somatochlora semicircularis (Mountain Emerald)
Smaller (<=45mm); male superior appendages straight, parallel or converging; female with vulvar lamina larger, longer than segment 9..........6 - Spots on side of thorax round, about same size..........Somatochlora minor (Ocellated Emerald)
Anterior spot on side of thorax conspicuously longer and thinner than posterior one..........Somatochlora walshii (Brush-tipped Emerald)
Libellulidae (skimmers)
- At least one pair of wings conspicuously patterned with black, brown or yellow to orange covering 1/4 or more of wing area..........2
Wings clear or with yellowish tinge or dark spots covering considerably less than 1/4 of wing area..........10 - Wings with large patch of color at base only..........3
Wings patterned more extensively, with color beyond midlength as well..........5 - Black or brown and yellow, with black or mostly brown basal wing patch..........4
Red to yellow, with yellow to orange basal wing patch..........Sympetrum occidentale (Western Meadowhawk) - Both wings with extensive basal spot..........Libellula luctuosa (Widow Skimmer)
Only hind wing with extensive basal spot..........Tramea lacerata (Black Saddlebags) - Each wing with dark marking covering most of basal half and dark spot at tip..........Libellula luctuosa (Widow Skimmer)
Marked otherwise..........6 - Each wing with a broad black band beyond midlength, extending more than 1/3 length of wing..........Plathemis lydia (Common Whitetail)
Each wing with a spot or narrow band at midlength, extending no more than 1/4 length of wing..........7 - Two black marks on each wing..........Libellula forensis (Eight-spotted Skimmer)
Three black marks on each wing..........8 - White spots between each black wing spot..........Libellula pulchella (Twelve-spotted Skimmer)
No white spots on wings..........9 - Larger (>=45mm); abdomen dark in center, yellow on sides..........Libellula pulchella (Twelve-spotted Skimmer)
Smaller (<=40mm); abdomen dark with whitish spots along sides..........Plathemis lydia (Common Whitetail) - Body entirely or partially blue or white (with powdery pruinose bloom)..........11
Body with no blue..........13 - No dark markings at wing base; face green..........Erythemis collocata (Western Pondhawk)
Dark markings at wing base; face not green..........12 - Eyes and face brown; pruinosity white, restricted to front of thorax and base of abdomen..........Ladona julia (Chalk-fronted Corporal)
Eyes green, face white; pruinosity blue, more extensive..........Pachydiplax longipennis (Blue Dasher) - Body green..........Erythemis collocata (Western Pondhawk)
Body not green..........14 - Body entirely brown; hind wing with conspicuous dark spot at base..........15
Not so colored; if small basal wing spot, then body not brown..........16 - Brown spot at midlength on wing..........Libellula quadrimaculata (Four-spotted Skimmer)
No spot in middle of wing..........Pantala hymenaea (Spot-winged Glider) - Abdomen black, longitudinally striped with yellowish above..........Pachydiplax longipennis (Blue Dasher)
Abdomen not as above..........17 - Body mostly black or dark brown (can be marked with yellow, white or red)..........18
Body mostly pale, yellow or red..........28 - Front of thorax paler than sides, separated from them by darker line..........Ladona julia (Chalk-fronted Corporal)
Thorax not as described..........19 - Face entirely or partially dark..........Sympetrum danae (Black Meadowhawk)
Face conspicuously white, or at least entirely pale..........20 - Abdomen with yellow dot only on 7th segment..........Leucorrhinia intacta (Dot-tailed Whiteface)
Abdomen with red markings or most segments spotted with yellow..........21 - Red or yellow spots on middle abdominal segments..........22
Red only on base of abdomen (may be very fine line on middle segments..........27 - Male..........23
Female..........25 - Pale marking on abdominal segment 7 extends to tip of segment..........Leucorrhinia borealis (Boreal Whiteface)
Pale marking on segment 7 extends no more than two-thirds length of segment..........24 - Pale spot on segment 7 as wide as long..........Leucorrhinia intacta, Dot-tailed Whiteface
Pale spot on segment 7 longer than wide..........Leucorrhinia hudsonica, Hudsonian Whiteface - Pale marking on abdominal segment 7 extends to tip of segment..........Leucorrhinia borealis (Boreal Whiteface)
Pale marking on segment 7 extends no more than half length of segment..........26 - Pale spot on segment 7 as wide as long..........Leucorrhinia intacta (Dot-tailed Whiteface)
Pale spot on segment 7 longer than wide..........Leucorrhinia glacialis (Crimson-ringed Whiteface), L. hudsonica (Hudsonian Whiteface), L. proxima (Belted Whiteface); structural characters necessary - Inferior appendage about half length of superiors..........Leucorrhinia glacialis (Crimson-ringed Whiteface)
Inferior appendage about two-thirds length of superiors..........Leucorrhinia proxima (Belted Whiteface) - Dark markings at base of each wing (visible at close range)..........Sympetrum illotum (Cardinal Meadowhawk)
No dark markings at wing base (may be yellow tinged)..........29 - Larger (>=43mm); entirely yellow to orange..........Pantala flavescens (Wandering Glider)
Smaller (<=40mm); variously colored, often with conspicuous black markings..........30 - Front edge of wing golden on veins or membrane, contrasts with rest of wing..........31
Front edge of wing same color as remainder..........33 - Sides of thorax plain (rarely marked with darker markings)..........Sympetrum costiferum (Saffron-winged Meadowhawk)
Sides of thorax with two pale spots (may be almost obscured by red pigment in mature males)..........32 - Pterostigma all dark; abdomen without light spots..........Sympetrum madidum (Red-veined Meadowhawk)
Pterostigma bicolored; abdomen with light spots low on side..........Sympetrum corruptum (Variegated Meadowhawk) - Well-defined pale stripes on each side of thorax..........34
Sides of thorax plain, or with spots, or with complex pattern of black and yellow..........35 - Abdomen with conspicuous white markings..........Sympetrum corruptum (Variegated Meadowhawk)
Abdomen without white markings..........Sympetrum pallipes (Striped Meadowhawk) - Two well-defined yellow spots low on each side of thorax; pterostigma bicolored..........Sympetrum corruptum (Variegated Meadowhawk)
No well-defined yellow spots on thorax; pterostigma one color..........36 - Abdomen with no black..........Sympetrum vicinum (Autumn Meadowhawk)
Abdomen marked low on sides with black..........37 - Sides of thorax with complex pattern of yellow and black..........Sympetrum danae (Black Meadowhawk)
Sides of thorax plain or with faint pattern..........38 - Face whitish; wing veins dark..........Sympetrum obtrusum (White-faced Meadowhawk)
Face and wing veins reddish..........Sympetrum internum (Cherry-faced Meadowhawk)