Olivia Watts from the Field Studies Council explores the hidden underwater world of dragonflies.
Dragonflies are large, vibrant insects that have been around for over 300 million years, long pre-existing the dinosaurs! They are regularly seen in summer, darting above ponds and rivers, but did you know they spend most of their life underwater?
Dragonfly life cycle
These insect giants can be seen across the UK, flying near bodies of water during the day. The UK is home to a variety of dragonfly species, each with slight variations in feeding, habitat preferences, and lifecycle. However, all dragonflies undergo these main life stages: egg, larvae, and adult.
Of these life stages, the longest is when they spend most of their life underwater as larvae (also called ‘nymphs’). This can be between one and five years, depending on the species. Adult dragonflies typically live for one or two weeks, but some live for up to eight weeks.
The larvae have six legs, a head with large eyes, an abdomen and an extendable jaw. They are typically duller in colour than the adults, supporting tones of brown and green. It is unlikely that you will see the larvae unless you go looking for them, but a quick pond dip can result in some amazing finds!
Ferocious feeders
Both adult and larval dragonflies are carnivorous. The larvae are ferocious hunters and predate other aquatic life, from tiny water fleas to larger prey like tadpoles and fish.
One adaptation that makes them such successful predators is their extendable hinged jaw, which will project forward at high speed to capture prey in the blink of an eye.
Dragonfly exuviae
When ready to transform into adults, the larvae crawl out of the water and find a suitable place to emerge from their exoskeleton, which is the hard outer casing of an insect. The emergence process is delicate, and the emerging adult is extremely vulnerable to predators because their wings are soft, and they cannot fly until they have hardened.
Once it has flown away, all that is left is the thin, fragile, outer casing of the larvae, known as the exuviae. A close look at this reveals where features like their eyes and jaws once were. You can also see a hole in the exuviae where the adult emerged.
Finding the alien-looking exuviae on a pond’s edge indicates dragonflies are completing their lifecycle there. With the right knowledge, they can also be identified to species to narrow down what lives in your pond.
Frequently Asked Questions
Q. Do damselflies also spend part of their life underwater?
A. Yes. Damselfly nymphs look similar to dragonfly nymphs but are daintier, with feather-like gills (caudal lamellae) at the end of their bodies.
Q. When can you see the larvae and exuviae?
A. Dragonfly larvae can be found underwater year round, and pond dipping is a great activity for finding them. The exuviae can be found on the water’s edge from late spring into summer, with some of the last adult dragonflies emerging in August.
Interested to learn more about dragonflies?
You can find out more about these fascinating insects with courses and guides provided by the Field Studies Council: www.field-studies-council.org
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