Next time you are sitting peacefully at the edge of one of the many Cavern dams – either admiring the tranquil beauty around you, or maybe fretting at the lack of fish bites – have a closer look at the lovely dragonflies flitting so effortlessly about you.
The first thing to note is that there are actually two different designs, one called a dragonfly and the other, smaller and more delicate, a damselfly. The chunkier dragonfly has two pairs of wings and the fore- and hind-wings are noticeably different in shape, the round eyes are lumps that seem to merge and take up the whole of the front of the head. There are big dragonflies and there are small ones, but they all share this pattern.
The tiny, slim damselflies also have two pairs of wings, but there is no difference between the fore-and hind-wings. The eyes are much smaller bumps and they appear to be stuck on at each side of the front of the head. They flutter about while the bigger and tougher dragonflies zoom with great speed and determination.
Males and females of both families can be told apart easily; as with birds the males are far more brightly coloured. It is the males that hold a tiny territory along the water’s edge and alight on reeds and grass stems to display their beauty to a passing lady. When he sees a lady of his species looking interested, the male will swoop and clasp her tightly behind her neck with specially designed hooks at the base of his abdomen and whiz her around his territory encouraging her to curl her abdomen round to collect sperm from a special sperm-sac on the underside of his thorax where he has already deposited some sperm. This looks to us like a very complicated manoeuvre but it seems to work for them!
Once her eggs are fertilized the male releases her and guards her fiercely while she lays her eggs. They all need water for the egg and nymph stages, but different species choose different places to lay the eggs. Some just drop them into the water, some place each egg carefully under floating vegetation, and others actually cut a slit into a reed and place the eggs there, from where the nymph can drop into the water on hatching.
These fairy-like creatures are in fact fiercely carnivorous and a large species will happily devour an unsuspecting smaller cousin. More usually they perform the useful service of eating mosquitos. If you encounter one away from the water’s edge, it will undoubtedly be a female, as they will wander far and wide in their search for food, while the males are tied to the water and their territory. Their life span is governed by the strength of their wings – once the fabric is torn or worn, it is sadly ‘tickets’. Thus as winter approaches we see fewer and fewer, for they need strong wings and the warmth of the sun to fly. As spring bursts forth so does the next generation of these enchanting creatures.
Sally Johnson