(Ordinal name from Greek, odous = tooth, referring to the toothlike labrum of the adult.)
This order includes many large and spectacular insects. Only about six per cent of species are Australian, but these include some remarkable forms. Adult Odonata typically have a more or less elongate, slender body and highly developed powers of flight. They hunt by sight and seize their prey (flying or sessile insects) while on the wing. Most are between 30 and 90 mm long, but they include some huge forms exceeding 150 mm and some small, fragile species less than 20 mm. The larvae (sometimes inappropriately referred to as nymphs) almost always are aquatic. They lie in wait for, or sometimes actively stalk, small prey, which are seized by shooting out the long, prehensile labium on which the palpi are modified for grasping.
All adults have short antennae composed of straight segments (filiform), prominent compound eyes and three simple eyes (ocelli). The mandibles are well developed and lie behind a toothlike, divided labrum. The legs are used to capture aerial insects by forming a "basket" in which the prey is secured before being transferred to the mouth. The two pairs of wings are large, membranous and equal in length (in all Australian species) with a complex venation. In damselflies (suborder Zygoptera) the forewings and hindwings are narrow at their bases and almost identical in shape and venation. In dragonflies (suborder Anisoptera) the wing bases are broader, and more so in the hindwing. Most dragonflies rest with their wings outspread perpendicular to the body (resembling aircraft wings) or else slightly depressed, but in one Australian subfamily they are held upright above the body. This attitude is also common in newly emerged adults of several families. Most damselflies rest with their wings closed. In this position the wings, anatomically, are straight up above the dorsum, but the usual impression is that they lie back along the abdomen since the pterothorax in Odonata, and particularly in damselflies, is very oblique. Three Australian damselfly families buck this trend by resting with wings held at right angles to the body, and species in certain other Australian families often rest with their wings partly open, so wing position at rest is not an infallible guide to classification. A second partial guide is that damselflies tend to be rather delicately built compared to dragonflies, but again Australia is home to several spectacular exceptions. Anatomical characters that accurately separate the suborders include wing shape, wing venation, and features of the genitalia in adults and the gills in larvae. A prominent characteristic of all odonate larvae is the grasping lower lip (labium) lying under the head, often extending back between the legs. With this organ a larvae can secure quite large prey including tadpoles and small fish. The number of larval moults, typically 10-15, is not constant within species but may vary with food and other growth conditions. Wing buds appear from about the 6-8th instar and develop gradually. Mature larvae leave the water to moult to the adult stage. Their exuviae can be found on reeds, tree trunks, stones or other objects. Larval life spans vary from a few weeks in some pond specialist species to a few years for some species in cold, upland situations. Adult life span is typically one season, at the least a few weeks and at most a whole summer. A very few species are known to hibernate and adults of these may fly on sunny days in midwinter.
General accounts of the order include those of Corbet (1980, 1983, 1999) on biology and Fraser (1957), Davies (1981), Davies and Tobin (1984, 1985) and Bridges (1994) on systematics. Silsby (2001) wrote a good general account at an anecdotal level. Schorr et al (2009) maintain a world species list. Calder (1999) last updated the Australian Faunal Directory listing, which incorporates the catalogue data of the Zoological Catalogue of Australia (Houston and Watson, 1988) but using family names that are not or never were widely accepted. Watson et al (1991) wrote a field guide to the Australian species, and Theischinger and Hawking (2006) wrote another although it too uses some non-accepted family and genus names.
In recent years the family-level taxonomy of Odonata has become much confused. New families or names have been proposed on little or no evidence and without proper revisionary studies. The worldwide scientific community has rejected most such names but in Australia some have been adopted on government-sponsored websites (e.g., Calder, 1999) and elsewhere (Hawking and Theischinger 1999; Theischinger and Hawking 2003, 2006; Theischinger 2002). Various small genera have been treated as families in order that Odonata become informative about water quality or the aquatic environment in national water sampling schemes within which macroinvertebrates of all orders are identified only to family level. An example is the AusRivas program (http://ausrivas.canberra.edu.au/). This usage of rejected names involving the adoption of an ecology-based taxonomy is confined to Australia. We here follow Rowe (2009) and international practice as exemplified by Schorr et al. (2009) by using names that are meaningful in the context of a natural (i.e., a phylogenetic) classification of the order.
The table below compares our family-level system with that of Theischinger and Hawking (2006), and with the current Australian Faunal Directory listing (Calder, 1999). Below the table is a list of names rejected and the reasons for rejection.
Accepted name Name used inTheischinger and Hawking 2006 Name used in the Australian Faunal Directory (Calder, 1999)
Suborder Anisoptera Suborder Epiproctophora, infraorder Anisoptera Suborder Epiproctophora (formerly Anisoptera)
Aeshnidae Aeshnidae Aeshnidae
Austropetaliidae Austropetaliidae Austropetaliidae
Corduliidae Austrocorduliidae Austrocorduliidae
Gomphidae Gomphidae Gomphidae
Libellulidae Libellulidae Libellulidae
Petaluridae Petaluridae Petaluridae
Synthemistidae Synthemistidae Synthemistidae
Suborder Zygoptera Suborder Zygoptera Suborder Zygoptera
Calopterygidae Calopterygidae Calopterygidae
Chlorocyphidae Chlorocyphidae Libellaginidae
Coenagrionidae Coenagrionidae Coenagrionidae
Diphlebiidae Diphlebiidae Diphlebiidae
Hemiphlebiidae Hemiphlebiidae Hemiphlebiidae
Isostictidae Isostictidae Isostictidae
Lestidae Lestidae Lestidae
Lestoideidae Lestoideidae Hypolestidae
Megapodagrionidae Megapodagrionidae Megapodagrionidae
Protoneuridae Protoneuridae Protoneuridae
Synlestidae Synlestidae Synlestidae
Rejected names: reasons for rejection
Odonata traditionally have been classified into two main extant orders, Anisoptera and Zygoptera, with a third suborder Anisozygoptera for two species in one genus (not Australian) that show an intermediate morphology. A number of fossil species also are inferred to have this morphology. The extant Anisozygoptera are sister to Anisoptera but to add in the fossil species would make Anisozygoptera paraphyletic. One taxonomic solution would be to create a new suborder for Anisoptera plus Anisozygoptera, reducing Anisoptera to an infraorder, but this changes the classification of more than half the extant species. A second solution would be to divide Anisozygoptera in two parts, one for the extant species, the other for fossil species. This would require a new suborder name for the two extant species. A third solution is to widen the concept of Anisoptera so as to include the extant Anisozygoptera, as was already done by Pritykina (1980). Bechly (1996, 1996-2008) adopted the first option, creating suborder Epiproctophora, but in the interests of nomenclatural stability it is better to follow Pritykina and assign
(Nepal, Japan) to Anisoptera, if paraphyletic constructs involving fossil taxa must always be avoided.
: Aeshnidae traditionally is divided into several subfamilies but there does not seem any good reason to separate out the two Australian genera
as a separate family, and they most likely are not each other's sister taxa. The family-level characters given by Bechly (1996-2008) for his family Telephlebiidae are "median space crossed", but it is not crossed in
, and "hypertriangles crossed" but that also applies to other genera of Aeshnidae.
: The Australian genera
(2 spp.) and
(1 sp.) together with South American genera
(1 sp.) and
(6 spp.) have been doubtfully separated from South American
(1 sp.) by a larval character in
that is most likely convergent with Libelluloidea. Australian species were originally described in
and the adults of all genera are very similar.
now finds itself in a separate superfamily because of the labial character, but that assignment is questionable. Accepting it for now, until it can be tested, there is no reason to divide off one of the three Australian species in Austropetaliidae as a separate family Archipetaliidae. Bechly (1996-2008) distinguishes
by (1) the eyes marginally more separated (by the width of an ocellus) than in either Neopetallidae or Austropetaliidae (within which this character is quite variable, even within species), (2) veins RP2-MA straighter (as in
), and (3) the wing spots a browner shade of red. Bechly's diagnostic wing characters for Neopetaliidae comprise four he says are convergent with both Austropetaliidae and Archipetaliidae, and two he says are convergent with other aeshnoid families. Most likely this entire set of genera are closely related and all we see is Gondwanan vicariance at genus level.
e: This family was created for five Australian genera and one South African genus united by three wing vein characters that are also found in two other families (
Bechly 1996-2008) of his Corduliidae complex. Loss of a secondary antenodal vein, a reduced number of Cu-A crossveins, and presence of a "pseudo-anal" crossvein are all shared with both Gomphomacromiidae and Pseudocorduliidae, and appear often in the broader group containing Cordulephyidae, Oxygastridae, Corduliidae, Hemicorduliidae, and Libelulidae. Bechly himself comments that his "family" may be paraphyletic. There is no reason to treat the genus
as separate from Corduliidae.
: A family comprising
from West Africa together with the four spp. in Australian genus
. The connection seems to be that these all are small species and the wing vein triangle is characteristically 4-sided, as occurs also in certain small libellulids. To combine these genera in a taxon at any level is implausible. There is no reason to split
: Bechly (1996-2008) gives a number of putative synapomorphies for this family but all are said by him to be convergent with the other families in his corduliid complex. According to Bechly's Hennigian estimate of phylogenetic relationships this family is sister to his corduliid complex, but neither of the two included genera has been examined using molecular markers. The family is constructed by clustering South American
(5 sp.) with Australian
(2 sp.) and Bechly himself suggested it is paraphyletic. There is no reason to split
from family Corduliidae.
: This family is a classic Bechly creation. The members can be recognised, according to Bechly (1996-2008), by synapomorphic characters "wing venation characters not yet known", and "other characters not yet known". Thus, there is no reason whatsoever to treat its two component genera, the Australian
, as anything other than Corduliidae.
: This taxon has had a chequered history as a separate family or else a subfamily of Corduliidae. It is a monophyletic group comprising four genera and 126 spp. with a worldwide distribution. If treated as a family it leaves a paraphyletic Corduliidae, and so, until the remainder of that family can be sorted out, it is best regarded as a subfamily within Corduliidae.
: This Bechly family is made up of
from Europe and
from eastern Australia. The defining features are said to be "wing vein characters not yet known" and "larval abdomen with medio-dorsal setae" (Bechly, 1996-2008), the problem being that the larvae of
do not possess such setae. (This larva was unknown when Bechly proposed the family.) Clearly, then, there is nothing to unite these two genera as a family and no reason to split
: The family was raised for the Australian genus
(2 spp.). Defining characters are the same as are said to define Gomphomacromiidae, Austrocorduliidae and various other parts of the Corduliidae complex (Bechly, 1996-2008), and said to be convergent in all these lineages. There is no evidence on which
can be split from family Corduliidae.
: These are a group of Gomphidae commonly recognized as a tribe or subfamily. Bechly (1996-2008) treats them as a family and gives several distinguishing characters that he says are convergent with a second gomphid subfamily, Hageninae that he raises to superfamily level, or else convergent to other gomphid genera. There is no evidence on which to recognize Lindeniinae/Lindeniini as a family outside of Gomphidae.
: These are small libellulids with a reduced "open" venation and "other characters not yet known" (Bechly 1996-2008). There are four Australian spp. in three genera, worldwide 22 spp. in four genera. Urothemistinae has long been treated as a subfamily of Libellulidae. Bechly (1996-2008) raises it to family status but to do so renders Libellulidae paraphyletic.
: A small damselfly,
with the general wing venation of the much larger Synlestidae except insofar as reduction in size appears to have been accompanied by some loss of veins. Bechly (1996-2008) proposed that certain vein characters were potential synapomorphies with the South American Perilestidae but instead of placing this species sister to Perilestidae he placed it sister to the entire superfamily Lestoidea and invoked multiple reversions to account for the non-appearance of various characters in the other families. A more parsimonious explanation both of the morphological and biogeographic evidence is that this is a small synlestid.
Predacious Palaeoptera with two equal or subequal pairs of wings; complex accessory genitalia developed from S2 and S3 of male. Larvae almost always aquatic, having an elongate prehensile labium modified for seizing prey, and respiring either by tracheal gills developed as internal folds of the rectal wall, or by external caudal appendages.