Comox Valley Naturalists Society
Knowing Nature . . .
September 18, 2007
We heard a rattling flutter before we saw them, wings glistening, skirting the edge of the pond. Crimson meadowhawks, sky-blue darners, metallic-green emeralds,
Dragonflies are some of the largest and flashiest insects around. What better way to spend a late summer day, than out at the pond watching these spectacular fliers. Dragonflies belong to a classification of insects known as Odonata, which is Greek for “toothed jaws”. The Odonata are from a line of ancient insects. Imagine traveling back in time 300 million years, to the Carboniferous period. The forest is warm and swampy, and overhead, is a dragonfly with a 70 cm wingspan! Fossils of these gargantuan dragonflies have been found. Smaller dragonflies, practically identical to our present day ones, are also part of the fossil record.
Anatomically, dragonflies share the characteristics of all insects, having a head, thorax and abdomen. Dragonflies have powerful jaws used to crunch insect prey. The rest of the head is made up of a small brain, two small antennae and two huge eyes. Each eye, called a “compound eye” has up to 30 000 lenses. This affords a 360-degree field of view. A narrow neck connects the head to the mid-section, or thorax. On top of the thorax are 4 wings. Dragonflies are fantastic fliers, and can reach speeds of 60km/hr. Each wing is independently controlled allowing for ultimate maneuverability. Dragonflies can fly up, forward, sideways and backwards. Beneath are six legs, which form a basket, used to scoop up prey. The long, narrow “tail” section of the dragonfly is actually the abdomen, where the reproductive organs are. The abdomen also helps the dragonfly balance in flight.
Life is ephemeral (short) for adult dragonflies, which only live a month or two. The dragonfly spends its early life underwater as a larva or nymph. Hatching from a small egg, nymphs are dull greenish-brown and grow to be 2-3 centimeters long. They are voracious, eating masses of tiny aquatic insects. Nymphs moult their skin often, about 10-14 times, and develop with each successive molt. Most of the dragonfly’s life is spent in the larval stage, typically about a year. After the final moult the dragonfly climbs up out of the water on a plant stalk, then eases out of its larval skin. The body expands and hardens during this process. The wings, shriveled at first, also expand. Dragonflies are very vulnerable at this time, and any disturbance, such as a boat wake, can result in death. Dragonflies leave behind their last moult on the plant they emerge from. Known as an exuvia, these empty larval cases can be found on plant stalks around the water’s edge.
Life as an adult dragonfly isn’t only short, it’s dangerous! As the dragonfly takes its first weak flight as an adult, birds are often waiting to take advantage of easy prey. The main purpose of the adult life stage is to find a mate. Male dragonflies often patrol a territory, looking for females. When mating, dragonflies fly in tandem, making a wheel formation. A couple may stay together this way until the female lays eggs. At the end tip of the female’s abdomen is an organ called an “ovipositor”. The female may oviposit eggs directly into water, or on soil or plant matter.
Out at the pond, there are smaller insects, which look like mini dragonflies. These are not young dragonflies, as dragonflies are fully-grown when they emerge as adults. These smaller relatives are damselflies, which are also members of the Odonata. Damsels are much smaller and more slender than dragonflies. When resting, their wings are held together, back over the body, whereas dragonflies spread their wings out flat. Damselflies also have eyes that are spaced much wider apart than dragonflies.
Dragonflies and damselflies are easily found from spring through late fall near freshwater ponds, marshes and peat lands. Wetlands are vital to these insects, which cannot breed in other habitats. Unfortunately wetlands are often filled in for human development. Due to habitat loss, 15% of dragonfly species are at risk of extinction in North America. Locally, a good spot for dragonfly watching is Woodhus slough, near Salmon Point Pub between Courtenay and Campbell River. Dragonflies are beautiful to watch and warm sunny days are best for viewing. There are sixty-four species found in BC, and they come in a broad range of colours and patterns. Go out and have a look!
Click on a link below to view the CVNS newspaper column.