Dragonfly

Dragonflies are highly specialized flying insects. They belong to the infraorder Anisoptera. This group is part of the larger order Odonata. There are approximately 3,012 known species of dragonflies. Most of these species live in tropical regions. However, they are found on every continent except Antarctica.

They are important predatory insects. They hunt both in the water and in the air. Many populations are currently threatened by the loss of wetland habitats.

The anatomy of an adult dragonfly is complex. Their bodies consist of three main segments: the head, the thorax, and the abdomen. The head is dominated by two large compound eyes. These eyes are made of many tiny units called ommatidia. For example, the species Aeshna interrupta has 22,650 ommatidia in each eye.

The thorax serves as the engine for flight. It contains powerful muscles that move two pairs of wings. The wings are long and membranous with many veins. These veins carry haemolymph, which is a fluid similar to blood. The hindwings are broader than the forewings. This characteristic is why the name Anisoptera means "unequal wing."

Dragonflies are much more agile than their relatives, the damselflies. Damselflies belong to the infraorder Zygoptera. While they share a similar body plan, damselflies are usually lighter in build. Most damselflies hold their wings folded over their bodies when resting. In contrast, dragonflies hold their wings flat and away from the body.

Dragonflies are also masters of aerial combat and hunting. They can use a technique called motion camouflage to attack prey or rivals. This allows them to remain difficult for targets to detect during flight.

The life cycle of a dragonfly involves distinct stages. They begin as a prolarva before becoming an active nymph, also called a naiad. These nymphs live in aquatic environments. Some nymph stages can last for as long as five years.

Once they emerge as adults, their lifespan changes significantly. Most adults live for about five weeks or less. Some species may only survive for a few days.

During the adult stage, they are fast, agile hunters. Some species are even capable of migrating across entire oceans.

Dragonflies have a very ancient evolutionary history. They belong to the group Palaeoptera, which means "ancient-winged." This name refers to the fact that they cannot fold their wings against their bodies. Their distant relatives, the Meganisoptera, lived 325 million years ago during the Upper Carboniferous.

These "griffenflies" were much larger than modern dragonflies. One relative, Meganeuropsis permiana, had a wingspan of about 70 centimeters. True dragonflies first appeared during the Early Jurassic period.

Reproduction in dragonflies is a uniquely complex process. It involves indirect insemination and delayed fertilisation. During mating, the male uses claspers on his abdomen to grasp the female behind the head.

The female then curls her abdomen under her body. She picks up sperm from the male's secondary genitalia located at the front of his abdomen. This specific movement forms a shape known as the "wheel" or "heart" posture.

This process also involves intense sperm competition among males.

Human culture has long been influenced by these insects. They appear in pottery, rock paintings, and Art Nouveau jewellery. In Japan, dragonflies are symbols of strength, courage, and happiness. However, European folklore has sometimes viewed them as sinister.

Different cultures also use them for practical purposes. In Indonesia, they are caught for food. In Japan and China, they are used in traditional medicine. Their beautiful flight and colors have even inspired poets like Lord Tennyson.