What is Odonata?
Three suborders in order Odonata.
Odonata constitutes a widely distributed order of insects. The some 5500 species belong to three suborders: the Anisoptera (dragonfly), the Zygoptera (damselfly) and the Anisozygoptera. In Japan, there are 217 species and subspecies belonging to these three suborders. The Anisoptera, which is called 'TOMBO (except Aeshnidae)' or 'YAMMA (Aeshnidae)' in Japanese, has such features as follows: the shape of fore wing being different from that of hind wing; typically large and active; robust body and wings; and wings opening while perching. The Zygoptera, which is called 'ITO-TOMBO (except Calopterygidae)' or 'KAWA-TOMBO (Calopterygidae)' in Japanese, has such features as follows: four similar shaped wings; small and inactive; slim body and wings; and wings usually closing while perching. The Anisozygoptera has only one genus, Epiophlebia, which has only three species in the world. In Japan, Epiophlebia superstes ('MUKASHI-TOMBO' in Japanese) is distributed, which is one of the most well-known insects all over the world, although it is one of relatively common species in Japan.
Left : Macromia amphigena amphigena belonging to Suborder Anisoptera; Center : Epiophlebia superstes belonging to Suborder Anisozygoptera;
Right : Mnais costalis belinging to Suborder Zygoptera.
What is Odonata?
Copulation and Oviposition
Males usually wait for females near/by the water. There are many species which form a territory at this time. When a male finds a female, he rushes for her to grasp her and to form tandem which is so-called 'O-TSUNAGARI' in Japanese. They copulate after forming tandem and then the female begins to oviposit being guarded by the male.
Left : A male Sinogomphus flavolimbatus wating for females with perching.
Right : A male Sinogomphus flavolimbatus grasping a female coming to lay eggs.
Left : Copulation of Ischnura senegalensis. Right : Single endophytic oviposition of Ischnura senegalensis.
Left : Gurading oviposition of Orthetrum melania. Right : Tandem endophytic oviposition of Lestes sponsa.
Odonates generally lay eggs in the plant tissue in, or above, the water (endophytic), or directly onto the water (exophytic). All Zygopterans, which have 'a perfect ovipositor', lay eggs in the plant tissue. Females of Aeshnidae (Anisoptera), which also have a perfect ovipositor, lay eggs in various substrate, such as live plant tissue, dead plants or mud.
Left : A pair of Sympetrum darwinianum laying eggs above the grass onto the mud (arrow: an egg).
Right : A female Polycanthagyna melanictera laying eggs into rather dry mud near water.
What is Odonata?
Egg development
Eggs hatch in a period of from some 10 days to more than 100 days after being laid. The duration of egg stage shorter than ca. 40 days is called 'direct egg development', i.e. eggs which hatch promptly without diapause, and that longer than ca. 80 days is called 'delayed egg development', i.e. those which hatch only after a prolonged period greatly exceeding that needed normal morphological development.
The latter is adapted to survive the inclement period such as winter or drought season. In Japan, Sympetrum, Lestes and Aeshna fall into the latter type. They generally lay eggs in autumn; overwinter in egg stage; and hatch during from spring to early summer. The former, on the other hand, includes dragonflies which breed in spring or summer and generally overwinter in larval stage.

What is Odonata?
Larval development
 Larvae are generally aquatic. They moult 9 to 14 times until emergence. Duration of larval stage is various: the shortest one is about 30 days and the longest one about 6-8 years.
Left : A larva of Aeshna juncea juncea which has swelling wing sheath.
Right : A full grown larva of Anax nigrofasciatus nigrofasciatus just before emergence breathing in the air.
There are various morphological types in this stage, which are as the result that adaptive radiation has taken place. It is said that the morphological and ethological adaptations shown by larvae to their environment are associated with one of three processes, i.e. respiration, feeding and concealment. For example, there are two types of respiratory organs, 'rectal gills' and 'caudal gills'. The Anisoptera and Anisozygoptera have the former type, and the Zygoptera has the latter. Dragonflies do not have a pupal stage.
Left : An anisopteran larva, Somatochlora uchidai, without caudal gills. Right : A zygopteran larva, Copera annulata, with three caudal gills.
What is Odonata?
There are two types of emergence, i.e. upright type and hanging type. Calopterygidae, Coenagrionidae, Platyenemididae, Lestidae, Petaluridae and Gomphidae fall into the former, and Epiophlebiidae, Cordulegastridae, Aeshnidae, Corduliidae and Libellulidae into the latter.
Left : Hanging type emergence: Sympetrum frequens.
Right : Upright type emergence: Trigomphus interruptus.
What is Odonata?
Adult stage
After emergence, adults move from their emergence site. The distance of the movement is various among species. An extreme example is the case of a cosmopolitan species, Pantala flavescens, which crosses the ocean from south to Japan. Another longer example is the case of Sympetrum frequens, or 'AKI-AKANE' in Japanese, which migrates to high land about more than 100 km far from the emergence site. Adults return to, or seek for, the water when they are mature.
Left : An immature male of Mnais costalis parching on the forest floor.
Right : A cosmopolitan species Pantala flavescens migrating over the Ocean.
Mature males are usually found by the water. They perch or fly to find females: called perchers or fliers respectively. The most species of mature females are hardly found by the water, however, which usually perch for a rest in the sunlight spot of wood or in grassland away from the water. Females come to the water only when they oviposit.
Left : A percher Trithemis aurora perching above the pond. Right : A flier Macromia amphigena amphigena flying above the small river.
Resting females. Left : Sympetrum gracile perching among trees. Right : Sinictinogomphus clavatus clavatus perching in the grass.
Adults are active and good at flying. Most of dragonflies and damselflies usually fly by counterstroking, that is, the beat cycle of fore- and hindwings are shifted by a half-cycle, so that whenever one pair of wings move down, the other is moving up (see the figure below). The flight of dragonflies is, thus, extremely rapid and straight.
Left : Counterstroking flight of Aciagrion migratum belonging to Zygoptera.
Right : Counterstroking flight of Epiophlebia superstes belonging to Anisozygoptera.
What is Odonata?
Odonates are carnivorous through their life without exception. They feed on small animals, such as Chironomus or Tubifex, in the larval stage, and, in the adult stage, on flying insects, sometimes relatively large ones such as cicadas. Their large eyes are convenient for catching their foods on the wing. Some anisopterans takeplace feeding flight in the twilight. Dragonflies such as Aeshna tend to go after moving materials in the air. 'BURI', or 'TORIKO', is a Japanese traditional method of catching dragonflies which utilizes the tendency.
Left : A Davidius moiwanus taruii preys on a caddisfly. Right : A Polycanthagyna melanictera was captured by 'BURI'.
Left : A Trigomphus citimus tabei preys on a damselfly Mnais pruinosa. Right : A Sieboldius albardae preys on a damselfly Calopteryx japonica.
Feeding frights in the twilight. Left : Aeschnophlebia anisoptera. Right : Anaciaeschna martini.
What is Odonata?
There are few odonates which complete thier life. Because most of them die from predation or other accidents, lifetime of adult odonates is relatively short, 10 days or so. Birds, spiders, or robber flies etc. prey on odonates. Moreover, many odonates nowadays get into traffic accidents. We often meet dead bodies of odonates, especially immature ones, on the road.
Left : Sympetrum croseolum was enmeshed in the spider's web. Right : A robber fly feeds on a dragonfly Stylogomphus suzukii.
Each died from a traffic accident. Left : Boyeria maclachlani. Right : Macromia amphigena amphigena.
. Left : Orthetrum albistylum speciosum was captured by a larva of Cicindela sp.. Right :A dead body of Sympetrum croseolum which might complete its life.