Eye for an Eye
Common Darter. Basically a flying surveillance system. D Pritchard
It’s not just the wings that make dragonflies and damselflies such successful predators, it’s the fact they’re attached to some of the best image capture systems that nature has come up with.
The arrangement of the large compound eyes can help you tell the difference between the two groups of insects. Damselflies have an eye on either side of a wide head, similar to a hammerhead shark. Dragonfly eyes wrap around the head and meet either in a point, or like a fighter pilot’s helmet.
Southern Hawker compound eyes, meeting broadly in the middle of the head. D Prichard
Banded Demoiselle, a damselfly with widely set eyes. You can see the three simple eyes in the centre of the head really clearly on this species. D Pritchard
Each of the compound eyes is made of up to 30,000 individual lenses in various sizes. These gather information in almost 360 degrees, and different parts of the eye can gather light in different wavelengths. As if that wasn’t enough, there are three other eyes in a triangular formation in between the compound eyes. These help the dragonfly to find the horizon and keep their heads level as they fly. Humans have two eyes and two optic nerves. Dragonflies have sixty thousands and three eyes (give or take), and an extraordinary number of optic nerves to process the information from those eyes.
It’s eight. Eight!
Amazingly, some of these are connected directly to the wings to speed up reaction time. The dragonflies can lock on to their prey and correct direction to keep aiming straight at it. They are able to predict the path taken by their food, and intercept it mid-flight. This gives them a 95% success rate. A cheetah is only successful up to half of the time.
We can’t even begin to comprehend the range of colours seen by dragonflies. Our own eyes are sensitive to three primary colours, and everything we see is made out of combinations of those three colours. Dragonflies can see between ten and thirty different core colours, many outside our own visible spectrum. They must see the world as if it were a kaleidoscope, and colour almost certainly forms a large part of how they identify and interact with each other.
A Migrant Hawker’s eyes showing a grid effect, caused by light reflecting from the thousands of individual lenses at different angles. D Pritchard
In fact, sight is a dragonfly’s most powerful sense, which is why they don’t have large antennae like butterflies. They use smell and pheromones to interpret the world around them.
Many dragons and damsels have a distinctly different appearance between sexes, either through colour or pattern. The age and maturity of Blue Tailed Damselflies leads to some wonderful variations, and you can see them around the sensory pond in good numbers just now.
Blue Tailed Damselfly in the sensory garden. D Pritchard
Some of them will use this to their advantage. Broad Bodied Chasers are notorious for this: a young male looks like a female so that they don’t get chased away by dominant males. On the flip side, a mature female starts to turn blue after egg laying, so that makes leave them alone. A quiet life is a longer life when you’re a female dragonfly!
Watch out for this around the visitor centre. There have been some Broad Bodied Chasers breeding around the new garden pond, and the females are starting to show some of these changes.
Now is a really good time of year to appreciate the range of species at Old Moor, with many of the early species still on the wing, and the late summer species appearing or expected over the next couple of weeks. These humid, warm days will encourage a lot of nymphs to leave the water and emerge as winged adults, so get out there and see what you can find!