The Whole Equals the Sum of Its Parts
Dragonflies and damselflies make up the insect order Odonata. The name Odonata comes from the Greek word for "toothed". It refers to the teeth on the mandibles of dragonflies. The Odonata can be further divided in the true dragonflies (suborder Anisoptera) and damselflies (suborder Zygoptera).
Like all insects, dragonflies and damselflies have six jointed legs, three major body parts (head, thorax, and abdomen), and a pair of very short antennae. Unlike butterflies and moths, dragonflies and damselflies have no scales on their wings and the wing veins can be seen clearly.
The head of a dragonfly bears two large compound eyes, two antennae, a powerful pair of mandibles, and a lower jaw-like structure called a labium. The compound eyes provide a field of vision that extends above, ahead and to the sides of the dragonfly. The eyes are so large that in many of the larger species the eyes cover almost the entire head. The antennae are used in flight to detect air speed and direction, and to determine the temperature of possible egg-laying sites. The mandibles are wedge-shaped and stout, and are used for chewing. When a dragonfly is eating its prey, the prey is held in the labium and chewed with the mandibles.
The body part immediately behind the head is the thorax. Both the wings and legs are attached to the thorax. It consists of three segments which are all slanted backwards causing the legs to be brought forward and the wings pushed backwards. This is critical to the dragonfly's hunting because it puts the legs in position more under the mouth to catch prey from the air and bring it to the mandibles to chew. The thorax also houses the muscles that propel the wings in flight. There are two pairs of wings--a pair of forewings and a pair of hindwings. The damselflies' forewings and hindwings are similar in size and shape; in fact, the name Zygoptera means "same wings". The forewings and hindwings of the dragonflies are different in size and shape, and accordingly, the name Anisoptera means "different wings". The wings contain many veins, which provide structural support. These veins can be easily seen and are used in the identification and classification of Odonata. In fact, the major veins all have commonly accepted names, as you can see in the diagram.
The abdomen is the major body part behind the thorax. It contains ten segments, and houses the organs necessary for digestion and reproduction. These organs include those necessary for mating, and in the case of the females, the organs necessary for laying eggs. At the end of the males' last segment are the anal appendages. These appendages are used to grasp the female behind the head during mating. Each species has differently shaped anal appendages, so they are very useful in identifying many species of dragonfly.