Dragonflies & Damselflies

Dragonflies and Damselfies have existed on Earth for somewhere in the region of 325 million years, making them some of the most ancient creatures we share the planet with. The oldest fossils belong to the order Protodonata, some of which had wingspans of around a metre! These are the ancestors of modern dragonflies and damselflies and were in evidence during the time of the dinosaurs.

The dragonflies and damselflies we see today belong to the order Odonata which comes from the Greek word meaning ‘toothed one’ - reference to their serrated jaws. The Odonata are split into two suborders, the dragonflies (Anisoptera, meaning unequal wings) and damselflies (Zygoptera, meaning equal wings). One of the questions that I’m most often asked is what are the main differences between dragonflies and damselflies? Although many aspects of their biology and life cycles are similar, there are a few diagnostic characteristics that will help separate them:

·         When at rest, damselflies hold their wings closed whereas dragonflies hold them open. Here’s an interesting fact; dragonflies don’t close their wings at all during their lives once they have emerged and their wings are fully hardened.

·         Damselflies are smaller and are generally daintier than dragonflies; their flight is also weaker and shorter. Damselflies make brief flights returning to rest on foliage, never travelling far. In contrast, dragonflies spend a lot of the day on the wing; their flight is much stronger, and some disperse over quite large areas.

·         Finally, look at the position of the eyes. Damselflies have eyes that are positioned quite far apart on either side of their heads. When seen peering around grass stems to me they really are quite adorable! In contrast, a dragonfly’s eyes are larger and situated close together, almost touching in most species, practically affording them complete 360 degree vision. Did you know that dragonflies have the largest eyes in the insect world?

Worldwide there are over 6,500 named species, but in the UK we have only a fraction of this number with around 40 breeding species. However, owing to climate change we have started to see the range of some of these insects spread in recent years, and more species are being recorded in some areas as the local conditions are altered. 

Dragonflies and damselflies are bound to water bodies and wetland areas for breeding and these are the best places to look for them.  From ponds to lakes, canals, ditches, bogs, flushes and even streams and rivers, different species have different requirements for breeding. Our garden ponds can provide suitable habitats for some species, another excellent reason for making a pond an integral part of your garden – preferably devoid of fish.

They are truly fascinating animals with incredible life cycles and are remarkably adapted to their lives on the wing. Often described as nature’s helicopters, dragonflies and damselflies are astonishing aerial acrobats and voracious predators, both in larval and adult form. If you are ever lucky enough to study one of these animals at close quarters, you will soon understand what makes them such efficient predators. Dragonflies have several incredible adaptations that contribute to them being the amazing aerial predators they are.

There are a range of colours across the dragonfly species and many include a metallic or iridescent colour. This is actually a combination of structural colours and pigment colours (yellow, red, brown and black). The blue colours are created by the reflection of blue light off micro-structures in the cuticle, whereas the green colours are created by a combination of a yellow pigment colour with a blue structural colour.

A newly emerged adult is called a ‘teneral’. If you happen to find one, you will notice that the colours are often muted or pale in comparison to the adults as it takes a few days for the adults to develop their final colouration. Some species, like the Broad-bodied Chaser Libellula depressa, have a powdery looking appearance; this is called ‘pruinescence’ and is a fine, waxy bloom surface covering.

If you have just sat and watched a dragonfly as it patrols a pond or over a wetland area you cannot help but be amazed by their aerial skills. To be such accomplished fliers their wings have evolved several adaptations. On the leading edge of each wing they have a ‘wing mark’ known as a ‘pterostigma’; this acts as a weight and helps to stabilise the wings and prevent vibrations during flight. In addition to the pterostigma there is a rib-like ‘costa’ on the leading edge making it the strongest part of the wing, allowing them to cut through the air more efficiently. These wing adaptations allow dragonflies to reach speeds of up to 36km/h, beating their wings 30 times per second, changing direction rapidly in all planes and even hovering. This enables them to catch their prey on the wing in mid-air. If you get the chance to watch them in action, it really is a spectacle. But you need a sharp eye, blink and you’ll miss the moment they grab their next meal.

The difference in flight patterns and the position of the eyes previously described dictate that these two suborders hunt in slightly different ways. Damselflies have strong forward vision, a bit like us in fact. This means that their focus is on prey items directly in front of or above them and they generally lunge in a straight line. A dragonfly’s all-round sight allows them to spot prey items in a much wider field of vision; their strong, acrobatic flight enabling them to target prey from a wider range of positions.

On the subject of eyesight, here’s an interesting fact. Odonata have amazing colour vision. A human eye sees in what’s known as tri-chromatic vision, in other words we see colours as a combination of red, green and blue. This is down to three types of light-sensitive protein called ospins and is the most common combination in the animal world. Depending on the species, dragonflies and damselflies have been recorded to have between 11 and 30 visual ospins. This enables them to see ultraviolet and polarised light as well as the red, green, blue combination – on paper they have better colour discrimination than us!

Add these adaptations to six legs capable of grabbing prey and razor-sharp mandibles to rip them apart and you truly have a wonder of nature and an awesome killing machine!

We know that dragonflies and damselflies are marvellous predators themselves, but the predator often becomes the prey and they also form the diet of many different species. They are most vulnerable as they emerge from their larval form and in the first few days as adult dragonflies. In areas where you get large numbers of dragonflies emerging over a short period of time it is common to see birds such as the hobby congregate to take full advantage of this feast. Indeed, Hobbies arrive from Africa to breed in the UK timed with these mass emergences – these birds will need large amounts of protein to recover from their journey and to prepare for breeding. But many other bird species also rely on this food larder to raise their young. The newly emerged adults also full victim to various specialist species of spider, such as the Furrow Orb Weaver that weaves its webs in the vegetation close to the water and high up in the reeds specifically targeting passing dragonflies and damselflies. And they will often eat each other too….