Order ODONATA (Dragonflies & Damselflies)

Dragonflies are large, strong flying, brightly colored insects that belong to the order Odonata. They are found world-wide except for in extremely cold regions such as Antarctica, northern Canada and Asia, and Iceland. There are about 5,000 species of odonates.
There are three sub-orders in the Odonata:

Anisoptera (Dragonflies) whose hind and fore wings are a different shape. They rest with their wings held out.
Zygoptera or "damselflies", who are small and delicate and with both the fore- and hind wings being the same size and rest with they wings folded in.
Anisozygoptera, which resemble the Anisoptera, but share similar characteristics between both the Zygoptera and Anisoptera sub-orders.

Suborder Anisoptera

MORPHOLOGY

The Head: The head consists of six segments that contain different structures:

First segment -compound eyes
Second segment -antennae (consists of three to seven joints)
Third segment-none
Fourth segment-mandibles (teeth are extremely strong)
Fifth segment- first maxillae (jointed appendages not as strong as those of the mandible)
Sixth segment-second maxillae

The Thorax: The thorax of the dragonfly is highly specialized to meet the requirements of supporting powerful wings and the altered functions of the legs. There are three pairs of legs, one connected to each thoracic segment. Though the legs are short, they are of considerable strength and are covered with tiny spines.

The Abdomen: The abdomen of the dragonfly consists of ten segments. At the far of the abdomen is a set of anal appendages. The shape of the abdomen shape is always narrow and elongated.

LIFE CYCLE OF ODONATA

All Odonata share a common life cycle. First, eggs are laid in or near fresh water, depending on if the female possesses a complete ovipositor (if a female has a complete ovipositor, she is able to submerge herself and lay her eggs in plant tissues or decayed wood). In the following spring, the eggs hatch. The larvae pass through 11-12 larval stages. Almost always, the larvae are aquatic and prey on other small insects, fish or tadpoles. The larvae capture prey by means of hooks on their lower lip (labium), which is rapidly released to strike their prey.

Larval lives can last anywhere from several months to several years. In the last stage of development, several signs of metamorphosis occur:

wing-cases swell to accommodate the developing adult wings
the pigmented area increases as a result of developing eyes
tissue retracts from the long larval labium to build the short labium of the adult

Eventually, the larval gills become ineffective and the larva must swim to the surface in order to breath. Then the larvae find a support such as a rock where the adult can split its larval skin, emerge, and expand its wings and abdomen. At this point, the adult stage (which consists of a pre-reproductive phase and a reproductive phase) has commenced. Usually, these phases combined lasts anywhere from a few weeks up to 2-3 months.

During the pre-reproductive adult phase, the dragonflies are maturing sexually. This period could last anywhere from a few days to several weeks. At this time, the freshly emerged dragonflies leave the emergence site and begin to feed. Another change that occurs over this period is in body color. A distinct difference in color may develop between the two sexes, the male often appearing more colorful.

Not only do dragonflies mature during this period, they also disperse. Some stay close to the emergence site, while others may fly extreme distances in flocks. The two primary needs for dispersal are overpopulation and habitat requirements that differ from those of the larva.

The reproductive period begins when the adults show reproductive behavior. This is usually signified by a return to fresh waters similar to the ones from which they came. Males return first, followed by the females, who have developed a batch of eggs. When the two sexes meet, and if the female is receptive, they immediately begin mating. After the eggs are laid, both the male and the female leave the site and don't return until another batch of eggs have developed.

FOOD HABITS

Like their larvae, adult dragonflies are predators that feed on any animal that they can capture and masticate. There are two ways in which a dragonfly can capture their food: in flight or from a surface. While in flight they use their legs to capture prey and then transfer it to the jaws. Dragonflies feed on other dragonflies, insects, or invertebrates taken from plant stems.

FLIGHT

Odonata are agile day fliers that partake in two types of flight. Some are "perchers" that spend most of their time on the ground or on twigs and stems from which they fly to catch prey. Males also may leave to combat other males or to seduce females. Other dragonflies spend all of their active time in the air. Damselflies are usually "perchers," while dragonflies are usually more active.

CONSERVATION

The lost of habitat is the biggest concern facing dragonflies today. It is essential to maintain healthy environments to insure the survival of any dragonfly species. Not only does the habitat have to provide a sufficient amount of food, but water ecosystems must be in balance. Fresh water is essential in perpetuating the life cycle.