This is the time of year to spend some time by the pond at RSPB Flatford Wildlife Garden, or down by the nearby River Stour, looking out for newly emerging dragonflies and damselflies. Dragonflies were some of the first winged insects to evolve, around 300 million years ago. Back then, the higher oxygen levels enabled them to grow to huge sizes, with wingspans of up to 75cm! Modern day dragonflies belong to the order Odonata, meaning 'toothed ones'. Although much smaller than their prehistoric ancestors, they still look impressive when flying above the water on a summer's day, and at top speed can reach speeds of nearly 30mph!
There are 57 species of Odonata in the UK: 36 dragonflies and 21 damselflies. The dragonfly life cycle has three stages: egg, nymph and dragonfly. Most of its life is spent as a nymph; these are hard to spot as they stay underwater. They spend a few years in this stage, as a fierce aquatic predator. When the nymph is finally fully grown, it climbs up out of the water, using a plant for support. The skin on the back splits, while the adult dragonfly slowly emerges. Haemolymph (a fluid analogous to blood in vertebrates) is quickly pumped into the wings and body to expand them. The thorax needs to be 27°C before it can fly, so once the wigs have fully expanded, they increase the temperature of the thorax by whirring the wings. The dragonfly is then ready to fly off, leaving behind the empty larval skin. In the UK, the dragonfly stage lasts up to just 8 weeks.
You may have noticed that dragonflies have huge globular eyes that take up most of their head. In fact they have the largest eyes for their body size of any animal, and 80% of the dragonfly brain is taken up with visual information! The eyes are made up of 30,000 facets, giving them almost 360 degree vision. According to the New Scientist, they also have colour vision 'better than anything ever seen in the animal world'. With such amazing eyes as these, it's no wonder that they are such deadly predators of other flying insects!
Close up of wings of Four Spotted Chaser Dragonfly
Photo credit: Ben Andrew (rspb-images.com)
This handy spotter's guide features the most common British dragonflies and damselflies, some of which you may spot at Flatford.
RSPB Flatford Wildlife Garden is currently open every day from 10:30-4:30. The summer garden is full of life and colour; we hope to see you there soon!