What is an Odonate?

Odonates, the dragonflies and damselflies, are insects of the Order Odonata. Their large size, ease of viewing, interesting behaviors, and dazzling display of colors makes them one of the most attractive groups of insects for scientists and the public. Odonates have three body segments (head, thorax, and abdomen), two pairs of wings, and three pairs of jointed legs. A pair of large, compound eyes dominates the head. The fore and hind wings are roughly equal in size and attached to the thorax. The abdomen is elongated into a narrow, segmented cylinder. Distinctive appendages at the tip of the abdomen in males are used for clasping females during mating.

Odonate Life Cycle

The typical odonate life cycle includes an aquatic larval stage and a terrestrial adulthood. Males are often territorial, defending sections of shoreline, sometimes with striking aerial acrobatics. During mating, males and females of some species can be observed flying together in tandem flights.

Mating "wheel" of Enallagma recurvatum (Pine Barrens Bluet) at Ashumet Wildlife Sanctuary, Mashpee

After mating, females deposit eggs either directly into bodies of water (e.g., a pond, bog, or stream, depending upon the species) or by injecting them using an ovipositor into plant tissue in or near water. The eggs hatch into an aquatic larval stage called a nymph. The nymphs are typically voracious predators of smaller aquatic life, such as tadpoles, small fish, and invertebrates. After a period of development, the nymph climbs out of the water, splits its outer "exoskeleton" and emerges as an adult dragonfly. The newly emerged adult, termed a teneral, is fragile and unable to fly at first.

Like nymphs, adult odonates are also predators and use their large eyes to detect their prey—often at considerable distances. Although many remain near water as adults, some dragonfly species spend much of their time away from their natal water bodies. A few disperse great distances and even undertake regular migrations.

Dragonflies and Damselflies

Two suborders of Odonata occur in Massachusetts: Zygoptera–the damselflies and Anisoptera–the dragonflies.

Damselflies:

• typically hold their wings together above their thorax and abdomen when at rest
• smaller and more delicate than dragonflies
• eyes are widely separated on their heads and project to the side
• often fly weak and irregular

Dragonflies:

• hold their wings out in a horizontal position when at rest
• large and robust
• eyes are larger than in damselflies, sometimes touching each other along the midline of the head
• fly fast straight, and powerful

The Taxonomy of Odonates in Massachusetts

Over 180 species of Odonata have been recorded in New England. These are divided into 10 families as follows:

A checklist of all the Odonata species of Massachusetts is available at www.odenews.org/masslist.htm.

Funding for this project was initially provided by: