Sanctuary Odonates Monitoring

Ruby meadowhawk dragonfly © Joy Marzolf, Mass Audubon
Ruby meadowhawk dragonfly © Joy Marzolf, Mass Audubon

Odonates, more commonly known as 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. 

Appearance 

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.

Dragonflies vs Damselflies

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

Damselflies

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

Dragonflies

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

Life Cycle

The typical odonate life cycle includes an aquatic larval stage and a land-based (or terrestrial) adulthood.

Mating and Egg Laying

Dragonflies and damselflies may mate while flying together in mid air in “tandem flights.” Or they may mate while hanging on to vegetation. Males are often territorial, defending sections of shoreline, and chasing away other males, sometimes with striking aerial acrobatics.

After mating, females either deposit eggs directly into bodies of water (a pond, bog, or stream, depending upon the species) or inject them into plant tissue in or near water using an organ known as an ovipositor.

Eggs and Nymphs

The eggs hatch into an aquatic larval stage called a nymph. Nymphs are typically voracious predators of smaller aquatic life, such as tadpoles, small fish, and invertebrates.

Metamorphosis

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.

If you look carefully on vegetation along the edges of weedy ponds or on bridge abutments, you can sometimes find the shed exoskeleton of the nymph, called an exuviae.

Adults

Adult odonates use their large eyes to detect their prey—often at considerable distances. Although many remain near water, some dragonfly species spend much of their time away from bodies of water. A few disperse great distances and even undertake regular migrations.

Odonates in New England

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

Suborder Zygoptera (Damselflies)

Calopterygidae – Broad-winged Damselflies, 5 species
Lestidae – Spreadwings, 9 species
Coenagrionidae – Pond Damsels, 37 species

Suborder Anisoptera (Dragonflies)

Petaluridae – Petaltails, 1 species Aeshnidae – Darners, 22 species Gomphidae – Clubtails, 30 species Cordulegastridae – Spiketails, 4 species Macromiidae – Cruisers, 2 species Corduliidae – Emeralds, 22 species Libellulidae – Skimmers, 40 species