Although the term "dragonfly" is frequently used to describe the insect order Odonata, the two main suborders, Zygoptera and Anisoptera, are better designated by the use of separate English names, damselfly and dragonfly, respectively. Damselflies are smaller and usually more slender than dragonflies. Many damselfly species have brightly colored bodies, often metallic green, blue or red. The wings may be colorless and transparent or colorfully tinted. In some species only the males have colored and patterned wings, whereas those of the female are transparent. At rest damselflies hold their wings erect over the back.
Unlike dragonflies, damselflies are not strong fliers. Both groups have very short antennae, but compensate for this by having very good vision. As they have relatively feeble flight, damselflies are seldom found far from the water in which they breed. Ponds, ditches, marshes and canals with a thick growth of reeds and water plants are damselflies’ favorite habitat.
Adult male Azure damselflies have a head and thorax patterned with blue and black. They have an azure blue abdomen patterned with black markings. The marking on the second segment of the abdomen is U-shaped, separated from the segment's narrow terminal black band. (This distinguishes it from the Variable Damselfly where the U-shape is joined to the terminal band with a black line.)
Segments three to five are blue with broader black terminal bands, lacking the forward-pointing projection the upper surface which adult male Common Blue Damselfly has. Segment six has a similar pattern but with more restricted blue and a broader area of black, and segment seven is mostly black, with just a narrow blue area at the base. Segment eight and much of segment nine are sky-blue, forming a noticeable contrasting patch, but there are small dark markings on the rear upper side of segment nine, which adult male Common Blue Damselfly does not possess.
Adult female Azure Damselflies have a head and thorax pattern similar to that of the male, but with glittering, glossy green replacing the blue coloring. The abdominal segments are largely black in coloring, with narrow pale markings at the junction between each segment.
The nymphs are usually green with browner wing buds and lamellae. They develop in one year (two in the north), feeding among submerged vegetation and on small invertebrates.
Mature adults are seen frequently mating and laying eggs. It usually stays close to the vegetation around the pond or lake and flies from May to September.
This common Damselfly looks very like a Common Blue Damselfly, but a close look can distinguish the two. The behaviour is also different - unlike Common Blues, they rarely fly out over large stretches of water. They are not normally as common around August and September, June and July being the peak of their populations. Most insects frequently clean the eyes and antennae with the forelegs, much as a cat washes its face using its paws. Damselflies are particularly thorough cleaners. They not only clean the sense organs of the head but use the hind legs to clean the end of the abdomen. Often the abdomen itself is curved and raised so as to stroke the wings and divide them from each other. The probable reason for this is that the long, weakly muscled wings may get stuck together by drifting threads of spider gossamer.
Like dragonflies, damselflies are extremely active insects and require a steady food supply to preserve their energy levels. Adult damselflies feed on small insects, both in the air and at rest, and the larvae probably feed on small aquatic insects and worms. Although neither swift nor strong, adults usually hunt small flying insects on the wing, as dragonflies often do, and scoop their prey into their jaws using their long legs. They probably feed mainly on gnats and midges. Some kinds of damselflies perform courtship displays before mating. In the banded agrion, Agrion splendens, the male waits for a female to fly past and then signals to her by raising his body and spreading his wings. If this succeeds and she comes to rest near him, he performs an aerial fluttering dance backward and forward, facing her all the time, and then comes to rest and mates with her. The banded agrion is one of the species in which the wings are conspicuously colored in the male but not in the female, and it seems likely that this difference in the sexes is associated with courtship display. Coloration plays an important part in damselfly courtship. Bright colors signal a healthy mate whereas faded colors indicate that the insect may have passed its sexual prime. The method of mating used by damselflies and dragonflies is unique among insects. The opening of the male’s internal sexual organs is in the usual insect position, near the tip of the abdomen. Before mating he transfers sperm to a complicated accessory sexual organ on the underside of the front part of the abdomen, just behind the thorax. When pairing he first grasps the female’s neck with a pair of claspers at the tip of his abdomen. Both insects then bend their bodies so as to bring the end of the female’s abdomen into contact with the male accessory organ, and the sperm is transferred.
The female lays the fertilized eggs in the tissues of water plants through a sawlike ovipositor. This often takes place immediately after mating and sometimes before the male has released his hold on the female. In some species the two, coupled in this way, crawl down the stem of a reed into the water and descend together to a depth of 1 foot (30 cm) or more before the eggs are laid. The minute creature that hatches from a damselfly egg can neither swim nor crawl and is known as the prolarva or pronymph. Within a few minutes, sometimes almost immediately after hatching, it sheds its skin and the first active larval stage is produced. The larva spends its life in the water and grows by shedding its skin at intervals, as do most insects. The larva may molt between 9 and 15 times during the course of its growth and may reach a length of 2–2½ inches (5–6 cm). It has a long body, not unlike that of an adult damselfly in shape, though the larva has no wings. At its rear end are three leaflike external gills. These contain a network of minute tubes, or tracheae, into which oxygen diffuses from the water. Respiration also takes place through the skin, rectum and wing sheaths.
In temperate regions, the life cycle of most of the smaller damselflies takes a year to complete, while that of some of the larger species may take up to two years. In the Tropics, the development of damselflies is more rapid and there may be several generations in a year. When growth is complete, the larvae crawl out of the water up onto a stone or a plant stem. They wait for a short time, until the skin of the back splits. The wings are expanded and hardened and the insects are able to fly within an hour or two. The period of time that the larvae spend underwater varies between species and according to environmental conditions. Species that live in warm waters with plentiful food develop more quickly than those living in waters that are cooler or that lack nutrients. As a result, the larval stage may last for only 40 days or for as long as 6 years.
Several species of the genus Megalagrion, which are native to Hawaii, spend all or part of their time on land. The larvae of one species, M. oahuense, have hairy appendages instead of the leaflike tail gills common to other damselflies and are unable to swim.
- Media related to Coenagrion puella at Wikimedia Commons
- Data related to Coenagrion puella at Wikispecies
- Coenagrion puella - Azure Damselfly
- Azure Damselfly (Coenagrion puella)
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