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They have three pairs of legs, a pair of antennae and generally very evident wing pads. Both of these groups are found in the slower moving areas of a stream either on plants or buried in the bottom. They use the lower mouthpart (Labium) for catching prey. One easy way to tell these closely related groups apart is that the Damselfies have feathery gills protruding from their abdomen.

1a. Abdomen terminating in 3 caudal lamellae, longest more than 1/3 length of abdomen
(fig. 1); feathery gills protruding from their abdomen .........Zygoptera (Damselflies) 2

1b. Abdomen terminating in 3-5 stiff, pointed valves, longest less than 1/3 length of
abdomen (fig. 2); feathery gills not protruding ...................Anisoptera (Dragonflies) 5

2a. First segment of antennae at least as long as remaining segments combined;
prementum with deep and wide median cleft (figs. 3).....................Calopterygidae 10

2b. First segment of antennae much shorter than remaining segments combined;
prementum with at most an extremely small median cleft(fig. 4)..................................3

3a. Basal half of prementum greatly narrowed and elongate (fig. 5); unextended labium
reaches back to or past middle coxae........................................................Lestidae 4

3b. Basal half of prementum not greatly narrowed and elongate (fig. 6); unextended
labium reaches only to fore coxae.................................................Coenagrionidae 11

4a. In the trifid lateral lobe of the labium the upper notch is simple (fig. 7); caudal gills
with two well-defined and complete, dark crossbands.................................Archilestes

4b. In the trifid lateral lobe of the labium there is a serrated border within the upper
notch (fig. 8); caudal fins lacking 2 well-defined and complete, dark crossbands...Lestes

5a. Prementum flat, or nearly so (fig. 9), without stout setae...................……....................6

5b. Prementum spoon-shaped, covering face to base of antennae (fig. 10) and armed with
stout setae.........................................................................................................………..8

6a. Tarsi 2-2-3 jointed; antennae 4 jointed....................….........…..............Gomphidae 17

6b. Tarsi 3-3-3 jointed; antennae 6 or 7 jointed......................……...................................7

 

7a. Antennae thick; prementum parallel-sided in distal 2/3, abruptly narrows at base
(fig. 11)..............................……..............................................Petaluridae, Tachopteryx

7b. Antennae setaceous; prementum widest in distal 1/2, but not parallel-sided (fig. 12)
..................................................................................……….......................Aeshnidae 23

8a. Labium with large irregular teeth on distal edge of palpal lobes (fig. 13); very
hairy nymphs; lotic................................................Cordulegastridae, Cordulegaster

8b. Labium with no large irregular teeth on distal edge of palpal lobes (fig. 14)............9

9a. Head with a prominent, nearly erect, thick frontal horn between bases of antennae
(fig. 15); legs very long with apex of each metafemur reaching to or beyond apex of
abdominal segment 8......................................................................Macromiidae 30

9b. Head without a prominent frontal horn between bases of antennae; apex of each
metafemur not reaching apex of abdominal segment 8.............................................31 

fig. 15

10a. Prementum cleft almost halfway to base (fig. 16)...............…..............Calopteryx

10b. Prementum cleft only to base of papal lobes (fig. 17)............................Hetaerina

11a. Caudal lamellae 1/2 as broad as long; distal margin of each palpal lobe produced
into 3 pointed hooks, middle one shorter than end hook and usually about 1/2 as long
as movable hook (fig. 18)....................................................…….........................Argia

11b. Caudal lamellae not more than 1/3  broad as long (except in Amphiagrion); distal
margin of each palpal lobe with a comparatively small end hook; portion between
movable hook and end hook more or less truncate with little teeth (fig. 19).......…......12

12a. Hind angle of head angulate (fig.20).............................................….................13

12b. Hind angle of head broadly rounded (fig.21).....................................….............14

13a. Antennae having 5-6 segments; caudal lamellae widest in middle, 1/3 as broad as
long with thick setae on margins from base to apex........….....….................Amphiagrion

13b. Antennae having 7 segments; caudal lamellae widest distally, 1/6 as broad as long
with only a few, widely separated setae on margins............…........…........Chromagrion
 

14a. Prementum with 1 (or if 2, 2nd very small) dorsal seta(e) on each side of the median
line........................................................................................……..............Nehalennia

14b. Prementum with 2-7 dorsal setae on each side of the median line (fig. 22)............15

fig. 22

15a. Antennae having 6 segments................................................................Enallagma

15b. Antennae having 7 segments.............................................................................16

 

16a. No lateral spines on terminal abdominal segments..............................Anomalagrion

16b. Lateral spines present on terminal abdominal segments.................................Ischura

17a. Antennal segment 4 generally about 1/4 as long as hairy segment 3 (fig. 23);
mesothoracic legs closer together at base than prothoracic legs (ventral view)
......................................................................................…….....................Progomphus

17b. Antennal segment 4 vestigial or nearly so (figs. 24); mesothoracic legs not closer
together than prothoracic legs..............................................…….................................18

18a. Wingpads strongly divergent from longitudinal body axis....…..............Ophiogomphus

18b. Wingpads laid parallel along back...............…….....................................................19

 

19a. Body very flat; abdomen nearly circular in dorsal view; paired tubercles on top of
head (fig. 25)..........................………..................................................................Hagenius

19b. Abdomen nearly cylindrical; no tubercles on top of head......……..............................20

fig. 25

20a. Antennal segment 3 flattened and oval, usually nearly as wide as long (figs. 26)...........
.....................................................................................…….............................. Lanthus
20b. Antennal segment 3 more or less cylindrical (fig. 27).......................…....................21

21a. Abdominal segment 10 longer than wide; end hook on palpal lobe small, about size
of palpal teeth (fig. 28)..........................................................…....................Arigomphus

21b. Abdominal segment 10 shorter than wide; end hook on palpal lobe large, strong, and
curved inward (fig. 29)..........................................................................…...................22

22a. Tibial burrowing hooks well developed; palpal lobe of labium with 4-10 regular
teeth on inner margin following the longer curved end hook................................Gomphus

22b. Tibial burrowing hooks absent or vestigial; palpal lobe of labium with 1-4 shallow
teeth on inner margin following the longer, curved end hook.................................Stylurus

 

23a. Hind angle of head angulate (fig. 30).....................................................................24

23b. Hind angle of head rounded (fig. 31).....................................................................27

24a. Edge of palpal lobe of labium wide and squarely truncate on tip (fig. 32); tips of
paraprocts curved inward...............................................…....................................Boyeria

24b. Edge of palpal lobe of labium accumenate (fig. 33); tips of paraprocts straight...........25

25a. Epiproct about 2/3 the length of paraprocts.............................................Basiaeschna

25b. Epiproct about equal length as paraprocts..................................................…..........26

 

26a. Dorsal hooks on abdominal segments 7-9 (fig.34)....................................Nasiaeschna

26b. Dorsal hooks absent on abdomen............................................................Epiaeschna

fig. 34

27a. Lateral spines present on abdominal segments 6-9................................Aeshna (in part)

27b. Lateral spines present on abdominal segments 7-9 only (or if one is present on
segment six, it is extrememley small...............................................................…...............28

 

28a. Antenna longer than distance from its base to posterior margin of head.....Gomphaeschna

28b. Antenna shorter than distance from its base to posterior margin of head.....................29

 

29a. End hook on truncate edge of palpal lobe prominent (fig. 35)...............................Anax

29b. End hook not prominent (fig. 36).......................................................Aeshna (in part)

30a. Head widest across the eyes.....................................................…...............Macromia

30b. Head not as wide across the eyes as across the bulging hind angles................Didymops

 

31a. Middorsal hook, spine, or knob present on at least segments 6 or 7 of abdomen.........32

31b. Middorsal hook, spine, or knob lacking on segments 6 and 7 of abdomen.........…......43

 

32a. Middorsal hook, spine, or knob present on segment 9 of abdomen....................…......33

32b. Middorsal hook, spine, or knob lacking on segment 9 of abdomen............…..............37

 

33a. Lateral spines of segment 9 of abdomen reaching almost to tip of epiproct or beyond
.............................................................................……................. Corduliidae (in part) 35

33b. Lateral spines of segment 9 of abdomen not reaching beyond 1/2 the length of
epiproct......................................................................................................……..............34

 

34a. Each cercus about as long as epiproct; 6-8 palpal setae.............…………...................
………………………………..……………………Cordullidae, Somatachlora (in part)

34b. Each cercus about 1/2 as long as epiproct; 5 palpal setae (fig. 37)...........……............
............................................................…………………..........Libellulidae, Perithemis

fig. 37

35a. No lateral spines on segment 8......................…......……….................Williamsonia

35b. Distinct lateral spines on segment 8.........………….............................................36

 

36a. Middorsal hooks absent on abdominal segments 1-5 or 1-6….............Helocordulia

36b. Middorsal hooks present on abdominal segments 2-9 or 3-9................Epicordulia

 

37a. Each cercus 2/3 to equal length of paraprocts; 7 setae on palpal lobe of labium........
………................................................………...................Corduliidae, Dorocordulia

37b. Each cercus less than 2/3 length of paraprocts.......…........ Libellulidae (in part) 38

 

38a. 0-3 premental setae, all fine or inconspicuous..........…….........................Ladonna

38b. 7-21 prominent premental setae.......................………….................….................39

 

39a. Lateral spines of abdominal segment 9 straight and long, reaching to at least the tips
of paraprocts, and about twice middorsal length of segment 9...…………..........Celithemis

39b. Lateral spines of abdominal segment 9 less than twice the middorsal length of that
segment............................................……………………................................…..........40

 

40a. Eyes small, making up less than 1/2 the length of the head (not including the labrum
and clypeus); body with numerous long hairs...........…………….................…….............41

40a. Eyes large, on lateral margins of the head and making up more than 1/2 the length of
head (not including the labrum and clypeus); body with only scattered long hairs.……..…. 42

 

41a. Segments 7-9 of abdomen with brown or black shining middorsal ridges; ligula
crenulate (fig. 38)..................................…………………................…...............Plathemis

41b. Segments 7-9 of abdomen lacking dark middorsal ridges; ligula not obviously
crenulate...............................……………..........………..........................Libellula (in part)

fig. 38

42a. Middorsal hook present on segment 3; epiproct and paraprocts about equal in length
......................................................………………….....................Leucorrhinia (in part)

42b. Middorsal hook absent on segment 3; epiproct usually noticeably shorter than
paraprocts...................…………………...........................................Sympetrum (in part)

 

43a. Apical third of cerci and paraprocts strongly curved downward; 7-9 palpal setae......
……………….........................................................................Libellulidae, Erythemis

43b. Apical third or cerci and paraprocts straight or only slightly curved; palpal setae
varies.........................……………………..................................................................44

 

44a. Prominent lateral spines on abdominal segment 8, at least as long as the middorsal
length of that segment...........................……………...…............ Libellulidae (in part) 45

44b. Lateral spines absent from abdominal segment 8, or if present they are smaller than
middorsal length of that segment...…………………......................................................46

 

45a. Epiproct at least as long as paraprocts (fig. 39)...……….................................Pantala

45b. Epiproct shorter than paraprocts (fig. 40)...........…………..............................Tramea

46a. Tips of lateral spines of abdominal segment 9 extending beyond tip of epiproct..……....
…………………......................................................................Libellulidae, Pachydiplax

46b. Tips of lateral spines of abdominal segment 9 not extending beyond tip of epiproct…….
………………………….................................................................................................47

 

47a. Each cercus not more than 1/2 length of paraprocts; if eyes large, on lateral margins
of head and making up more than 1/2 the length of the head (not including the labrum
and clypeus) (fig.41), then lateral spines of abdominal segment 8 at least 1/2 the
length of that segment (middorsally)..........…………………..............................................48

47b. Each cercus more than 2/3 length of paraprocts (except in Sympetrum, where cerci
can be less than 1/2 the length of paraprocts and eyes large and on lateral margins of
head and making up more than 1/2 the length of the head (not including the labrum
and clypeus) (fig.41), but lateral spines of abdominal segment 8 are less than 1/3
middorsal length of that segment).........................……………………...............................49 

fig.41

48a. Eyes small, making up less than 1/2 the length of the head (not including the labrum
and clypeus) (fig.42); lateral spines of abdominal segments 8 and 9 roughly equal in
length; body very hairy; abdominal sterna lacking dark markings………..Libellula (in part)

48b. eyes large, on lateral margins of head and making up more than 1/2 the length of the
head (not including the labrum and clypeus) (fig. 43); body smooth to only slightly
hairy; dark markings present on abdominal sterna....………............Leucorrhinia (in part)

49a. Abdominal segments 4-9 with a median, dorsal bump bearing a tuft of thick setae;
found in brackish water.............……………........................Libellulidae, Erythrodiplax

49b. Abdominal segments 4-9 lacking a median, dorsal bump bearing a tuft of thick setae;
found in fresh water............................……………………............................................50

 

50a. Paraprocts roughly equal in length to epiproct........….....Libellulidae, Nannothemis

50b. Paraprocts longer than epiproct..................................……………........................51

 

51a. Thorax having a dark longitudianal stripe along its dorsolateral margin......……….........
.......................................……………………................................Corduliidae, Cordulia

51b. Thorax lacking a dark longitudianal stripe along its dorsolateral margin.....…….........52

 

52a. Crenulations of palpal lobes shallow (fig. 44); at least 9 palpal setae........…….............
………………..............................................................Libellulidae, Sympetrum (in part)

52b. Crenulations of palpal lobes deep (fig. 45); 7-8 palpal setae.................……….............
………………...........................................................Corduliidae, Somatochlora (in part)

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Sources.