Calopteryx splendens - The Banded demoiselle

A glittering jewel of Britain's Waterways 

By Lachlan Royle 

A female Banded Demoiselle that landed on me as some place to rest

Distribution 

The banded demoiselle is a common species of damselfly across much of  Wales and England, it is slightly scarcer found the further you head north but its range is ever expanding. Out of the 21 species of damselfly found in the UK they are one of the easier to encounter given you are in the right environment. 

Banded demoiselles like small slow moving bodies of water as well as completely still areas like ponds and lakes. They are particularly fond of areas with soft mud on the river or lake floor. As a result the biggest potential threat to banded demoiselle populations is pollution and surface runoff. 

Behaviour 

Banded demoiselle's life cycle, like many other invertebrates involves a larval stage. The larval form of this species reside in the mud at the bottom of streams and lakes for roughly 2 years feeding on other small aquatic invertebrates. Once ready to emerge the larvae will climb up on to a plant that emerges from the river and shed to reveal their wings. They are mostly active in the UK between the months of May and August. Once mated a female can lay up to 10 eggs a minute for 45 minutes, rather cunningly she will deposit these eggs sometimes under the surface of very thin leaves. Once hatched the larva return to the waterways to commence their two years of preparation for life as an adult. 

A male banded demoiselle 

Damselfly's of all species including Banded Demoiselles are voracious predators that are incredibly effective with a ridiculous 95% success rate when hunting, to put that in context a leopard one of the most stealthy and effective mammalian predators only has a success rate of  38% a ridiculous 57% lower. As a result damselfly's and dragonflies are the most successful hunters in the world. They are so successful it is estimated a single damselfly will eat hundreds of thousands of insects in the brief time it is alive as an adult. As a result damselfly species such as the banded demoiselle play an integral role in regulating other insects populations and maintaining a stable ecosystem. 

Damselfly species have been on the earth for millions of years due to how successful they are. They are an incredibly active group moving almost constantly during the day and picking off food on the wing, when resting however they fold their wings up tightly behind them, instead of fanning them out like their dragonfly cousins. Both species have differing flying patterns as a result, dragonflies are rather more acrobatic pulling off 'stunt' moves mid flight whereas a damselfly, such as the banded demoiselle has a much more delicate flight pattern often bobbing up and down with each flap of their wings. 

To surmise the banded demoiselle is a perfect example of the danger of beauty, whilst seeming on the exterior as a graceful and dainty invertebrate it is in fact a ridiculously skilled hunter and one we should be thankful is as small as it is.