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Dragonflies and damselflies

John W. H. Trueman and Richard J. Rowe *

     =============== Protodonata [Extinct] 
     |  ============ Protanisoptera [Extinct] 
<<===|  |
     |  |=========== Triadophlebiomorpha [Extinct] 
     |  |
     ===|     ====== Protozygoptera [Extinct] 
        |     ====== Archizygoptera [Extinct] 
        |     ====== Zygoptera 
              |  === Anisozygoptera 
                 === Anisoptera 

Containing clade(s): Pterygota top

Table of Contents

Characteristics: adults
Characteristics: larvae
Life Cycle and Behavior
Discussion of Phylogenetic Relationships


Odonata are an order of aquatic palaeopterous insects. There are about 6500 extant species in just over 600 genera. Adult odonates are medium to large in size, often conspicuous and/or brightly colored insects and are aerial predators hunting by sight. They generally are found at or near fresh water although some species roam widely and may be found far from their breeding sites. The larvae are predatory, aquatic and occur in all manner of inland waters.

In some countries, notably Japan, Odonata have long been a popular subject of art and culture, and rank with butterflies and birds as a topic of popular scientific interest. In the European folk tradition, odonates are generally accorded a less favourable status as "horse-stingers" or "devil's darning needles". In fact they neither sting nor bite and all species are completely harmless. If anything, Odonata are beneficial to humans because as voracious aquatic predators they assist in the control of insect pests.

To some extent the presence of odonates may be taken as an indicator of ecosystem quality. Local faunal composition may be strongly affected by any change in water flow, turbidity, etc., or in aquatic or waterside vegetation. The greatest numbers of species are found at sites which offer a wide variety of microhabitats.

Inland fishermen may know dragonfly larvae as "mud-eyes" and use them as bait. Adult dragonflies are a minor food item in some countries, and the larvae sometimes have been used to control pest insects (eg, mosquitos in domestic water tanks). But, for the most part, Odonata are of little economic importance. Their main attraction for humans is aesthetic.

The modern order is divided into two main suborders: Zygoptera (damselflies) and Anisoptera (dragonflies). The common name "dragonfly" also is used for the whole order. More than one-half of all species are tropical but odonates of both major suborders occur in every faunal region except Antarctica. A third suborder, Anisozygoptera, largely known from fossils, is represented by one extant species in Japan and one in the Himalayas.

Sympetrum corruptum. USA. Anisoptera; family Libellulidae. Photo: Larry J. Friesen
Copyright © 1997 Larry Jon Friesen, Santa Barbara City College

Epiophlebia superstes. Japan. Anisozygoptera; family Epiophlebiidae, emergent adult on its larval skin. Photo: Takashi Aoki
Copyright © 1997 Takashi Aoki.

Superfamily and family distributions in Odonata reflect ancient vicariance events such as the break-up of the southern continent Gondwana. Some genera and species are widespread. Others are highly local in distribution. Some families are restricted to cool streams or rivers, others to ponds or other still waters, and some to marshy places. The most species-rich and widespread family is the mainly tropical Libellulidae (Anisoptera). The most restricted is the monotypic Hemiphlebiidae (Zygoptera), only known from six or so small reedy pools in south-eastern Australia.

The fossil record for most modern families dates back to the Jurassic or else the Cretaceous period. Fossil species not assignable to any of the the three extant suborders are placed conventionally into one of four fossil suborders: Protozygoptera, Archizygoptera, Protanisoptera and Triadophlebiomorpha. A separate order, Protodonata, occasionally regarded as a suborder of Odonata, contains some very large to enormous Upper Carboniferous and Permian fossil odonatoid species. The largest of these "giant dragonflies", Meganeuropsis permiana, measured about 720 mm from wingtip to wingtip. The wingspan of modern anisopterans ranges from less than 20 mm (eg, Nannodiplax rubra, Libellulidae) to more than 160 mm (eg, Petalura ingentissima, Petaluridae): those of modern Zygoptera range from about 18 mm (eg, Agriocnemis pygmaea, Coenagrionidae) to about 190 mm (Megaloprepus caerulatus, Pseudostigmatidae).


Characteristics: adults

General: The head is large, concave behind, on a flexible neck. The compound eyes are large and either widely separated (all Zygoptera, some Anisoptera), just touching, or extensively fused along the mid-line. The face carries three ocelli and a pair of short, bristle-like antennae. The prothorax is small, the mesothorax and metathorax are large and fused into a single, strong pterothorax. The legs are weak, suited to perching and to holding prey but not to walking. The abdomen is long, rarely any shorter than the length of one wing, and flexible, with 10 visible segments, and terminates in clasping organs in both sexes. In Zygoptera the abdomen almost always is thin and cylindrical. Females of all zygopteran and several anisopteran families carry a prominent ovipositor under abdominal segments 9-10. Males always possess secondary genitalia on the underside of abdominal segments 2-3.

Resting attitude: The wing veins of Odonata are fused at their bases and the wings cannot be folded over the body at rest. Almost all Anisoptera settle with the wings held out sideways or slightly downward. Most Zygoptera settle with the wings held together, dorsal surfaces apposed. However, the zygopteran thorax is so oblique that when held in this way the wings fit neatly along the top of the abdomen. They do not appear to be held straight 'up' as in butterflies or mayflies. In a few zygopteran families the wings are held horizontally at rest, and in one anisopteran genus (Cordulephya, Corduliidae) the wings are are held in the typical damselfly resting position.

Wing venation: Adult Odonata possess two pairs of equal or subequal wings. There appear to be only five main vein stems. A Nodus is formed where the second main vein (subcosta) meets the leading edge of the wing. In most families a conspicuous pterostigma is carried near the wing tip.

Identification as Odonata can be based on the venation. The only likely confusion is with some lacewings (order Neuroptera) which have many crossveins in the wings. Until the early years of the 20th century Odonata were often regarded as being related to lacewings and were given the ordinal name Paraneuroptera, but any resemblance between these two orders is entirely superficial.

In Anisoptera the hindwing is broader than the forewing and in both wings a crossvein divides the discoidal cell into a Triangle and Supertriangle.

Wings of Archipetalia auriculata (Neopetaliidae)

Photo: J. W. H. Trueman
Copyright © 1997 J. W. H. Trueman

Rarely, the crossvein runs obliquely across the cell, causing either the Triangle or Supertriangle to appear four-sided.

In Zygoptera the two pairs of wings are almost exactly equal in shape, size and venation. There may be very numerous crossveins

Hindwing venation of Matrona japonica (Calopterygidae).

or rather few.

Hindwing of Austroargiolestes icteromelas (Megapodagrionidae).

The venation in Anisozygoptera is intermediate between that of the two major suborders.

Hindwing venation of Jurassic fossil species Heterophlebia buckmani.


Characteristics: larvae

The most obvious characteristic shared by all odonate larvae is a conspicuous grasping labium (lower lip: mask), used for capturing prey.

At rest the mask is held folded underneath head and thorax, extending back as far or further than the front legs and in some families far enough forward to cover the face below the compound eyes. In prey capture the labium is shot rapidly forward and prey is grasped with paired, hand-like palps.

Even from above and with the mask retracted, identification of larvae to order and suborder is very easy, based on several other features.


Life Cycle and Behavior

Odonate larvae are non-discriminate hunters which will eat any animal as large as or smaller than themselves, including their own species. Small vertebrates such as tadpoles and fish fry are not immune from attack. Prey may be stalked or ambushed. The labium is shot out by a rapid rise in haemolymph pressure. The prey is held with the hand-like palps and is withdrawn to be chewed by strong mandibles.

Almost all odonate larvae are aquatic. They occur in every sort of water body from soaks and seepages to streams and rivers, lakes, temporary pools and water-filled tree holes. A few species tolerate moderately salinity, a few others have semi-terrestrial larvae which roam across the surface of bogs and swamps at night. A half-dozen or so fully terrestrial larvae are known from distantly related families.

As they grow, larvae undergo approximately 10-20 molts, over a time between 3 months and about 6-10 years depending on species. Instar number is not always fixed but may depend on seasonal conditions and food supply. Wing pads develop externally from about the 6-7th instar. Metamorphosis is direct without a pupal stage and emergence takes place on a fixed support out of the water, sometimes a considerable distance from the water's edge. The newly emerged adult flies away from water for a few days to feed and mature, during which time the full adult color develops. Teneral (new) adults can be recognised by a glassy sheen of the wings. Additional color changes occur later in life in some species.

Adult Odonata are visually oriented hunters with exceptional aerobatic ability and extremely acute eyesight. Many are strong fliers, and to catch them can be extremely difficult. Males tend to congregate around the breeding sites where they may be seen either perched on waterside vegetation, hovering over small territories or hawking up and down in search of females. Females of many species spend much time away from the water, only appearing to mate and lay eggs, but some congregate with the males. Most adults are long-lived. In cold climates some over-winter in sheltered places and in the dry tropics some aestivate through the dry season. Some undertake long dispersal flights, including transoceanic journeys, but others remain tightly associated with their larval habitat.

Mating: Odonate mating is an elaborate process. The male clasps the female by the head (Anisoptera) or prothorax (Zygoptera). The pair then fly together in tandem (male in front, female behind), often to a perch. The female bends her abdomen forward and downward to form the 'wheel' position and connect with the secondary genitalia on segments 2-3 of the male, which previously have been charged with sperm from the primary genital opening on segment 9. Complex sperm displacement and sperm transfer activities then occur. A mating may last from several seconds to several hours, according to species.

In some species the pair lay eggs together, maintaining the tandem hold. In others the male hovers above the female while she lays her eggs. In some the male returns to his territory or perch while the female oviposits alone.

Xanthocnemis zealandica ovipositing (New Zealand)
Photo: R.J. Rowe. Copyright © 1997 R.J. Rowe

Eggs are laid into plant tissues on, above, or below the water surface, or, in species without a functional ovipositor, are deposited onto the water surface or inserted into sand or mud. Egg development mostly is direct (ie, without diapause) and eggs takefrom 7-9 days to several months to hatch, according to species. Egg-stage overwintering is common in temperate climates. The egg hatches as a 'prolarva' or 1st instar (actually a pharate 2nd instar) which wriggles to water if not already in it and then immediately undergoes ecdysis to the 2nd instar (first feeding, first free-living) stage. top

Discussion of Phylogenetic Relationships

Higher Relationships
The relationships of Odonatoidea (= Odonata plus Protodonata) to the other pterygote insects continues to be much debated. For an outline see the attached note on Pterygote higher relationships.

Subordinal relationships in Odonata
Within the order Odonata, debate rages on several fronts. Which suborders are monophyletic and which are paraphyletic? Which fossil groups are "ancestral to" or closely related to which modern suborders? Is Zygoptera the paraphyletic basal grade from which Anisozygoptera and Anisoptera have arisen or are Zygoptera and Anisoptera monophyletic groups, and is each derived from within suborder Anisozygoptera? There appears to be general agreement only that

Wing venation
Hypotheses of the phylogenetic relationships within Odonata depend critically on interpretation of the wing venation. Different schemes of wing vein homology across the suborders and alternative hypotheses of character-state transformation or polarity lead directly to different evolutionary hypotheses. Despite many efforts, consensus remains elusive. Attached is a brief note about differing views on Odonate wing venation.

Subordinal relationships
Consistent with their various conclusions on the evolution of the wing, different authors have proposed different subordinal phylogenies.

Handlirsch (1906-08) regarded Anisozygoptera as a "stem group" from which Anisoptera and Zygoptera arose as separate lineages. Tillyard (1928) regarded Zygoptera as basal, with Anisozygoptera derived from within Zygoptera and Anisoptera derived from within Anisozygoptera. Tillyard and Fraser (1938-40) treated Zygoptera and Anisozygoptera + Anisoptera as non-sister monophyletic groups, the former derived from Protozygoptera and the latter from Protanisoptera, but Fraser (1957) reverted to the Tillyard (1928) arrangement.

Hennig (1981) made Zygoptera the monophyletic sister group to Anisozygoptera + Anisoptera, and placed Anisozygoptera sister to Anisoptera. Carle (1982) followed Handlirsch (1906-08) in treating Anisozygoptera as basal but regarded both Zygoptera and Anisoptera as monophyletic. Carle and Wighton (1990) derived a polyphyletic Zygoptera by convergent reduction in the wing veins from anisopteran ancestors.

In recent years two cladistic parsimony analyses have been attempted. Trueman (1996 [1991]) found in favor of the Fraser "paraphyletic Zygoptera, paraphyletic Anisozygoptera" hypothesis. Trueman (1993) agreed -- although with less certainty as regards the zygopteran branching pattern. Further cladistic (parsimony) work is in progress by a number of authors.

In contrast, Bechly (1995, 1996), using a manual Hennigian (phylogenetic systematics) method, found in favour of a monophyletic Protozygoptera sister to the modern suborders, paraphyletic Anisozygoptera, monophyletic Zygoptera and monophyletic Anisoptera. Nel et al (1993), and Lohmann (1996), using similar methods, came to largely compatible results. (Bechly and Lohmann present their phylogenies largely under new names and with unconventional uses of existing names, so care must be taken when reading their papers.)

Thus, at the present time, the jury remains firmly out. Even so, convergence toward one of two rival phylogenies can be discerned. The pattern of relationships would appear to be either as Tillyard (1928), Fraser (1957) and Trueman (1996) have it:

     ============================= Protodonata
     |  ========================== Protanisoptera
=====|  |
     |  |  ======================= Protozygoptera
     ===|  |
        ===|          ============ Zygoptera (Coenagrionoidea)
           |          |
           =Zygoptera=|  ========= Zygoptera (Lestoidea, Calopterygoidea)
                      |  |
                      ===|  ====== Anisozygoptera (eg, Epiophlebia)
                            |  === Anisozygoptera (eg, Heterophlebia)
                               === Anisoptera

or else something approximately along the lines proposed by Handlirsch (1906-08), Carle (1982) and Bechly (1996). Using established names this may be represented as:

     ================================== Protodonata
     |  =============================== Protanisoptera
=====|  |
     |  |  ============================ Protozygoptera
     ===|  |
        ===|                  |======== Zygoptera
           |                  |
           ==Anisozygoptera===|  ====== Anisozygoptera (eg, Epiophlebia)
                              |  |
                              ===|  === Anisozygoptera (eg, Heterophlebia)
                                    === Anisoptera

. . . although within this broad group of phylogenies both the number and the ordering of branches within Zygoptera and paraphyletic Anisozygoptera are disputed. top


The established and widely accepted classification of extant families is as follows:







(Classification from Watson and O'Farrell, 1991)

Alternative classification schemes have been recently proposed which erect many new taxonomic divisions and coin new names for old categories. To maintain stability we recommend use of the established and generally accepted classification until such time as the superiority of one or another of the newly proposed forms can be clearly established. top


Bechly, G. H. P., 1995. Morphologische Untersuchungen an Fluegelgeaeder 
          der rezenten Libellen und deren Stammgruppenvertreter 
          (insecta; Pterygota; Odonata) unter besonderer Beruecksichtigung 
          der phylogenetischen Systematik und des Grundplanes 
          der Odonata. Petalura (Spec. Vol.) 1: 1-341.

Bechly, G.  1996.  The Phylogenetic System of Fossil and Recent 
          Odonatoptera.  Internet website http://members.tripod.de/GBechly/phylosys.htm 
          developed and maintained by the author.  

Carle, F. L., 1982.  The wing vein homologies and phylogeny of 
          the Odonata: a continuing debate.  Soc. int. Odonatol. 
          rapid Comm. 4, x+66 pp.

Carle, F. L., and D. C. Wighton, 1990.  Insects from the Santana 
          formation, Lower Cretaceous, of Brazil. 3. Odonata. 
          Bulletin American Museum of Natural History 195: 51-68.

Fraser, F. C., 1957.  A reclassification of the order Odonata. 
          Sydney.  R. Zool. Soc. NSW.

Handlirsch, A., 1906-08.  Die fossilen Insekten und die Phylogenie 
          der rezenten Formen.  Ein Handbuch fur Palaontologen 
          und Zoologen.  Leipzig.  Engelmann.

Hennig, W., 1981.  Insect Phylogeny.  New York.  Wiley.

Lohmann, H., 1996.  Das phylogenetische system der Anisoptera 
          (Odonata).  Entomol. Z. 106(6):209-252, 106(7):253-296, 

Nel, A., X. Martinez-Delclos, J.-C. Paicheler, & M. Henrotay, 
          1993. Les "Anisozygoptera" fossiles: phylogeneie et 
          classification (Odonata). Martinia (hors ser.) 3: 1-311.

Tillyard, R. J., 1928.  The evolution of the order Odonata. Part 
          1. Introduction and early history of the order.  Records 
          of the Indian Museum 30: 151-172.

Tillyard, R. J., and F. C. Fraser, 1938-40.  A reclassification 
          of the order Odonata.  Austr. Zool. 9: 125-169, 195-221, 

Trueman, J. W. H., (1993).  Toward a Phylogeny of Odonata.  PhD 
          thesis.  Australian National University.

Trueman, J. W. H., 1996 [1991].  A preliminary cladistic analysis 
          of odonate wing venation.  Odonatologica 25: 59-72.

Watson, J. A. L., and A. F. O'Farrell, 1991.  Odonata (Dragonflies 
          and Damselflies).  Ch. 17 in CSIRO (ed.) The Insects 
          of Australia. A textbook for students and research 
          workers.  560 + 600 pp. 2 volumes.  Carlton.  Melbourne 
          University Press.  pp. 294-310.

About this page

Special thanks to Takashi Aoki for permission to use the image of Epiophlebia superstes, and to Larry J. Friesen, Peter Marsack, Stephen Richards and Joseph L. Spencer for other images.

Line drawings copyright © 1997, John W. H. Trueman and Richard J. Rowe.

This page compiled by:

John W. H. Trueman
E-mail: trueman@rsbs.anu.edu.au.
Research School of Biological Sciences, Australian National University, Canberra, ACT 0200, AUSTRALIA

Richard J. Rowe
E-mail: Richard.Rowe@jcu.edu.au.
Dept. of Zoology & Tropical Ecology, School of Biological Sciences, James Cook University of North Queensland, Townsville, QLD 4811, AUSTRALIA

Correspondence regarding this page should be directed to John Trueman, at trueman@rsbs.anu.edu.au.

Page copyright © 1997 John Trueman & Richard Rowe

Last saved 20 February 2001

Title Illustration

Coenagrionid damselfly, Argia sp., North America. Photo: Joseph L. Spencer
Copyright © 1997, Joseph L. Spencer.

Information on the Internet

A growing number of organizations and dragonfly enthusiasts maintain websites about dragonflies. Substantial and notable sites, as of October, 1997, include the following:

International Organizations:
From 1971 until mid-1997 a single organisation, the Societas Internationalis Odonatologica (SIO), acted as a focus for dragonfly researchers and enthusiasts throughout the world. That organization disintegrated at its general meeting held in Maribor, Slovenia, in August 1997. It is replaced by two organizations. The Foundation SIO (FSIO) dates from June 1997 and has claimed all assets and publication titles of SIO. The Worldwide Dragonfly Association (WDA) is a new organization set up in September 1997 "to advance public education and awareness by the promotion of the study and conservation of dragonflies (Odonata) in their natural habitats in all parts of the world". Webpages of the two societies are as follows:

Comment and information on the split between WDA and FSIO can be found at the IORI site below.

Other notable Odonata pages:


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