The adult sombre goldenring is often seen resting near water, often quite low down and with the abdomen hanging almost vertically (2). Adults are seen between May and August (2) (3), and feed on small insects that fly along the stream (2). Like all dragonflies, the sombre goldenring is an agile predator, and its huge eyes give it excellent vision (6).
After mating, the female sombre goldenring lays eggs into the muddy bottom of a shallow stream or spring, thrusting the ovipositor into the mud to lay the eggs while in flight (2). One female of this species was observed to lay nearly 200 eggs (2). Unlike some other dragonflies (6) (7), the male sombre goldenring does not guard the female while the eggs are laid (2).
The sombre goldenring larvae live buried in mud, sand or gravel on the stream bed, with only the head, front legs and tip of the abdomen exposed. From this hidden position, the larva lies in wait for passing prey (2). Dragonfly larvae are formidable predators which catch their prey by shooting out the lower jaw, or ‘labium’. The labium is armed with hooks, which impale the victim and drag it back to the mouth as the labium is retracted (6) (7).
As a dragonfly larva grows, it goes through a series of developmental stages known as ‘instars’, before emerging from the water and moulting into the adult form. In the sombre goldenring, the larvae develop very slowly and only emerge as adults after about four or five years (2). As in the related golden-ringed dragonfly, the emergence of the adults probably takes place in spring (2). After it has emerged, an adult dragonfly will spend some time feeding and maturing before it breeds (6) (7). However, the lifespan of the adult sombre goldenring is short, lasting only several weeks (2).