Five Years Underwater: The Half of a Dragonfly's Life Nobody Photographs

A dragonfly spends most of its life as a nymph: a squat, drab, armoured predator walking around the bottom of a pond or stream. Depending on species and water temperature, that stage lasts from a few months to five years. The winged adult that everyone photographs generally lives a few weeks.

The nymph is not a passive stage. It hunts tadpoles, worms, other insect larvae and, when it can get away with it, small fish. Its weapon is a hinged lower lip called the labium, folded under the head and fired forward hydraulically in a few hundredths of a second. Fully extended it can reach a third of the nymph's body length.

It also has jet propulsion. Water is drawn into the rectal chamber, which is lined with gills for breathing, and expelled hard to shoot the animal forward. The same organ handles respiration and escape.

Emergence is the transition worth setting an alarm for. On a warm night the nymph climbs a stem clear of the water, grips, and splits along the back of the thorax. The adult hauls itself out, hangs while it pumps haemolymph into crumpled wings, and waits for them to harden. For an hour or two it is soft, pale and completely defenceless. By sunrise it is a dragonfly, and the empty nymphal skin — the exuvia — is still clinging to the stem, which is why exuviae are the best census tool a pond surveyor has.

If you want to know which species truly breed in a pond, do not count adults. Count the shells they left behind.