Odonata, damselflies

Odonata (dragonflies and damselflies)
The Odonata are an order in the phylum Uniramia or Hexapoda (depends which book you read), for more pages on this phylum click the menu below left.

Uniramia

--Centipedes

--Hexapoda 1 (insects)

--Hexapoda 2 (insects)

--Hexapoda 3 (insects)

--Identification to order level

--Insect orders

----Lepidoptera (butterflies, moths)

----Ephemeroptera (mayflies)

----Hemiptera (bugs, cicadas)

----Hymenoptera (bees, ants, wasps & saw flies)

------Bumblebees

----Coleoptera (beetles)

----Dictyoptera (mantids, cockroaches)

----Diptera (true flies)

----Neuroptera (lacewings, ant lions)

----Orthoptera (crickets, locusts)

----Thysanura (bristletails, silver fish)

----Strepsiptera (stylops)

----Thysanoptera (thrips)

----Odonata (dragonflies, damselflies)

----Trichoptera (caddis flies)

----Siphonaptera (fleas)

----Isoptera (termites)

----Phasmida (stick & leaf insects)

----Dermaptera (earwigs)

----Anoplura/siphunculata (sucking lice)

----Mallophaga (biting lice, bird lice)

----Psocoptera (book, bark, dust lice)

----Mecoptera (scorpion flies)

----Collembola (springtail)

----Embioptera (web spinners)

----Plecoptera (stone flies)

----Diplura (bristletails)

----Protura

----Zoraptera

Odonata fast facts

Large, with long bodies.
Large eyes with up to 30 000 ommatidia (facets).
Minute antennae.
Specialised mouthparts with strong teeth.
Two pairs of similar wings finely veined.
Both adult and nymph are predators. Nymphs aquatic and long lived.
5 500 species worldwide, 113 European, 40 British.
Hemimetabolous
Fossil record goes back over 300 years.

Odonata, dragonflies, damselflies, are also sometimes known as horse stingers, devil's darning needle, which according to superstition will be used to sew up the lips of liars. They are divided into two sub-orders: Zygoptera, the damselflies, and Ansioptera, the true dragonflies.

Wings and flight. The wings of the damselflies are alike, whereas the hind wings of the dragonflies are broader than the front wings (see Libellula depressa). At rest damselflies hold their wings vertically over their body, whereas true dragonflies rest with their wings spread out. In flight the wings operate independently, unlike those of other strong fliers, e.g. wasps and

bees who link both wings together. They are skillful fliers and can even fly backwards. Wind tunnel studies, partly financed by the U S Navy and Air Force, have found that they twist their wings on the downstroke. This creates miniature whirlwinds that move the air much faster over the upper wing surface, and so reduces air pressure and increase lift. Damsel flies usually have slimmer abdomens in both adults and nymphs. Both sub-orders usually fly during the day. During the Carboniferous there were huge dragonflies (with wingspans as large as that of a seagull today) to be found in what is now England. At that time insects were the only flying animals. It is believed that the huge dragonflies were slower fliers that those of today.

Left is a damselfly nymph, possibly Lestes sp. Note the leaf-like tail filaments and slimmer body. This one came as an egg in the stem of some plants I ordered for my pond. With the popularity of garden ponds increasing this may be a new method of dispersal. Adult

Lestes sp. fly from June until the first frosts.

The nymphs (see the damselfly nymphs above and right) are aquatic, carnivorous and sluggish. Damselfly nymphs are slender, with 3 leaf-shaped tails, and are much better swimmers than the fatter dragonfly nymphs. On hatching from the eggs the larvae start feeding at once. They have a prehensile lower lip (called the mask) which is folded under the head at rest (see the drawing of Agrion puella right). This has moveable teeth, and the whole thing can shoot out at great speed to grab prey. They tend to creep around the bottom of ponds and streams searching for prey. When a nymph is about to moult into an adult it crawls out of the water. Dawn or dusk during fine weather are the most common times for moulting. There are usually 10 - 15 moults as nymphs. It can take nymphs from 1 to 5 years to mature depending on species.

On the right is an Agrion puella nymph, with a more detailed drawing of the mask. All nymphs are carnivorous, and the larger ones will even catch tadpoles and small fish.

The adults are strong fliers and eat other insects, especially mosquitoes, black flies and other small flies, that they catch on the wing. They have a row of stiff bristles on either side of

their legs, so the three pairs form a basket to scoop flying prey. However because of the positioning of the front legs Odonata cannot walk or crawl. Damselfly flight speed has been recorded as 1.5 metres per second and 16 wing beats per second. Compare this with other insects.

Females and males of the same species are often different colours, and younger adults are usually a paler colour than older ones. The beautiful colours of the adults fade after death.

Coenagridae family. These are commonly known as the narrow-winged damselflies. Their adult body length ranges from 25 - 50 mm. On the left is Coenagrion pluella, the Azure damselfly or Pond damselfly. Its wingspan is 41 mm and body length 33 mm. The adult flies from May to August. It is found near water meadows with lush grass, canals with abundant reeds, ditches and is one of the most common found in garden ponds. It is common in England and Ireland, but less common in Scotland. This one was just moulting into and adult. The female lays her eggs in the tissues of plants on the water surface.

The venation of the wings is used in identification to species level, however there is disagreement between entomologists in naming the veins, so identification for a beginner is usually easiest using illustrations.

They have 10 or 11 abdominal segments. All males have a pair of claspers on segment 10, and their reproductive organs on segment 2 or 3. In females the ovipositor is in segment 8 or 9. Some females may have a pair of appendages on segment 10.

Before mating the male must transfer sperm from the genital opening on segment 9 to the reproductive organs on segments and 3. Then on finding a female he grabs her by the neck with his claspers. She curves her body around until the tip of her abdomen touches his reproductive organs in segment 2 and 3 to collect the sperm. This is known as the copulation wheel. After mating the pair may fly in tandem with the male leading. Females mate with more than one male and store the sperm from the matings, although she tends to use the sperm from the last mating. The male mating organ contains a structure that allows him to scrape or push aside the sperm from previous matings before deposting his own in the most favourable spot. The elngth of time he holds on to the female (the copulation wheel) will also prevent her mating with another.

The female places her eggs in the water, usually on the stems of aquatic plants. Some species actually crawl underwater to place their eggs deeper, some have a saw-like structure on the ovipositor to make slits in plants enabling them to place the egg inside the stem, and others just skim over the water dipping the tip of their abdomen in and scattering the eggs singly. In some species the male holds on to the female while she lays eggs. Adult life span can be as long as 2 months, but is usually no more than 2 or 3 weeks.

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