This page is regularly updated, please select here to view the latest version.
Here be dragons…….well maybe not at the Rec. But we have had sightings of the next best thing, those jewels of the sky; Dragonflies.
There have been 36 species of dragonfly recorded in the UK as well as a number of their smaller cousins, the damselfly. Dragonflies are renowned for their predatory skills and their amazing flight. This is made possible because they have two pairs of wings, each of which can move independently of one other. They also have huge flight muscles, which constitute up to 25% of their body weight. This combination enables them to perform incredible aerial manoeuvres, which include hovering, flying backwards and making sudden turns. It’s this agility that contributes to them being such efficient predators, as they’re able to snatch their insect prey in mid air.
Dragonflies also have phenomenal eyesight. They have large compound eyes, which as a proportion of their body size, makes them the biggest in the animal kingdom. They can see to the front, sides, above and below, and with only a slight turn of the head, behind as well. These huge eyes can pick up movement at quite a distance to identify potential prey. The eyes are also important in locating suitable habitats for mating. Special UV receptors in the eyes are able to pick up reflected polarization patterns created at the surface of water….a pretty neat adaptation!
Water is essential to the life cycle of dragonflies. They seek out suitable freshwater sites at which to mate and lay their eggs.
A pair of mating dragonflies adopt the ‘wheel’ (or ‘heart’) position. The male holds the female by the back of the head with his abdominal claspers and she curls the tip of her abdomen up towards him. Once fertilization has taken place, the female deposits her eggs in the water. You may have seen dragonflies flying low over the surface of a pond and dipping the tip of their abdomens in the water as they release eggs from the ovipositor.
The eggs hatch into larvae, of which only a very small proportion survive into adulthood. The larvae are also ferocious predators eating just about anything that comes their way, including tadpoles and sometimes, small fish. Interestingly, they actually breathe using gills in their rectum. The gills filter out oxygen as water is ‘pumped’ over their surface.
After several moults that allow the larvae to grow, they finally emerge from the water by climbing up a plant stem. Then swallowing air to increase the internal pressure in their bodies causes the exoskeleton to crack open at the back of the head and thorax. Gradually the adult dragonfly emerges, its soft body hardens up and it pulls itself free from its old skin. Body fluid is then pumped into the abdomen and wings, to expand the crumpled wings. This process can take up to 4 hours, during which the dragonfly is very vulnerable to predation. But assuming it survives, the adult will fly away to start the cycle all over again.
The dragonflies we’ve seen this year at the Rec have been the Broad-Bodied chaser, spotted earlier this year, and more recently, the very striking Golden-Ringed Dragonfly.
Newly emerged adults tend to move away from water initially. Maybe these were immature adults seeking shelter, or perhaps more mature creatures on the look out for a suitable breeding spot and partner. Either way they were very welcome
It’s a wonderful privilege to see these insects at the Rec. But just imagine how many more there would be if we had a pond………..as well as all the other wildlife it would attract. Definitely worth thinking about! Anyone got a spade and an hour or two to spare?!!
Words and pictures by Denise Long
Click each image to enlarge