Dragonflies and damselflies are amongst our most striking insects. Large, colourful and energetic, the sight of them flying over ponds, rivers, meadows and glades is synonymous with summer days.

Migrant Hawker dragonfly in flight © Liz Andrew

Dragonflies and damselflies belong to the insect order Odonata. The two groups are easily told apart when you know what features to look for. Damselflies are smaller and slighter, have a fluttering flight and can clasp their wings over their back at rest. Dragonflies hold their wings out straight like an aeroplane when resting or in flight, flying faster and more directly. At close range the eyes have it- damselfly eyes are widely spaced, giving good binocular vision to help them hunt amongst vegetation, whilst dragonfly eyes wrap around their head like a helmet, allowing them to spot prey all around them as they fly in the open. Both dragonflies and damselflies come in a variety of bright colours depending on the species and range in size from the 22mm Small red damselfly to the 78mm Emperor in the UK.

Dragonflies and damselflies are voracious predators of smaller flying insects. Their huge eyes help them to spot prey, which they catch using spiny legs and despatch with sharp, powerful mouthparts (the name ‘odonata’ means toothed jaws). Dragonflies have the highest success rate of any predator, catching around 95% of the prey they chase (compared to only 25% in lions!). Part of this is due to their agility, as they can control their four wings individually, allowing them to turn sharply and fly side-to-side, backwards and even upside-down! However, the real secret to their success is their mental abilities. A recent study found that dragonflies can calculate the speed and flightpath of a flying insect, allowing them to intercept their prey rather than chasing after it.

Adult dragonflies and damselflies have a brief but energetic life. They have only a few weeks or months to find a breeding place and reproduce. Males of many dragonflies aggressively defend a territory, whilst in damselflies it is usually a free-for-all, with hundreds of pairs seen flitting around ponds in summer. They mate in a heart shape, as the male uses the tip of his abdomen to transfer sperm to the base of the female’s. Males of many species then guard the female from competitors by gripping her neck with his tail claspers until she has laid her eggs. After this ordeal, it’s not surprising that females will sometimes feign death to avoid other mating attempts!

Young dragonflies and damselflies are known as nymphs or naiads after mythical water spirits. They live underwater, but their appearance is more alien than beautiful. Like the adults, the nymphs are predatory, but they employ different weaponry- extendible jaws! These jaws are hinged and hidden under the head. When an invertebrate, tadpole or small fish comes close, the nymph shoots its jaws out at a fraction of a second to snatch its meal. If faced by a larger fish, the nymph has a getaway trick at the other end- shooting water from its bottom to jet away!

The nymphs will develop for several months or years under water. When the time comes to ‘grow up’ one spring or summer morning, the nymph climbs out of the water for its final moult and the adult dragonfly slowly emerges. After pumping up its wings and drying out, the adult takes flight. The shed skins, known as ‘exuviae’ often remain clinging to the reeds.

There are over 50 species of dragonfly and damselfly in the UK, 17 of which can be seen at Hampstead Heath. Volunteer Monitoring since 2017 has provided an important picture of species populations in the Heath’s larger ponds. These dragonfly records provide an important indicator of the water quality and wildlife value of the ponds and help to assess the success of habitat creation measures as part of The Ponds Project completed in 2017.

Monitoring volunteers also discovered a newcomer to the Heath - the Willow emerald damselfly Chalcolestes viridis. This metallic green species is a recent arrival to the UK from mainland Europe, spreading across the South East. First found on the Heath in 2018, they have since spread to ponds across the Heath, where they lay eggs in willow twigs above the water.

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