We think we are so smart and that our creations are so very fantastic, but the truth is that even the humblest of living organisms makes our greatest creations look like toys. Dragonflies and damsel flies are ancient insects but they are very good examples of unbelievably refined flying machines that should make drone enthusiasts drool with envy!
Dragonflies are some of the most ancient of insects and their ancestors, the griffinflies, crop up in the fossil record of the Upper Carboniferous period of 325 million years ago (Mya). These massive insects had wingspans up to about 750 mm! Their size would appear to contradict theories concerning why modern insects are limited in their dimensions. The true dragonflies first appeared during the Early Jurassic of about 195 Mya. Humans have only been around for about 300,000 years but had they been there during the early days of the huge dragonflies then one of the reasons not to go swimming in a lake or pond would have been the risk of being attacked by 40 cm long dragonfly nymphs! Today there are thought to be upwards of 2,967 recorded species of dragonflies and 3,332 recorded species of damselflies – fortunately (?) the largest found in Europe have wingspans of about 100mm or so.
Dragonflies and damselflies both lay their eggs in fresh water. The lifespan of their nymphs can extend up to five years in large species, and between two months and three years for the smaller ones. The nymphs like the adults, are ferocious predators. Some are true hunters that crawl across the lake bottom, yet other species just lay in wait on, or burrowed into, the mud. More-or-less anything that moves nearby and that is small enough, will be snatched from the water in a lightning-fast strike. The nymphs of dragonflies have a modified underlip, the labium, that despite the inertial and drag forces encountered underwater, can be shot out and retracted again in less than an 1/8th of a second (video: https://tinyurl.com/y4t2zp8s). The labium can be up to a 1/3rd of the nymph’s body length. The nymph can also use jet-propulsion, building up water pressure in its abdomen and then shooting it out through its anus thus powering itself forward towards its prey. Other mouth-parts then wrap and hold the prey while the jaws crunch it up! The jet-propulsion mechanism is an adaption of the nymph’s breathing mechanism which involves water being pulled in through the rectum and passed over the gills. Jet-propulsion can also be employed by the nymph to escape from predators.
Adult dragonflies are amazing aerial acrobats. Flying at speeds up to 15 kms/h, they can turn in an instant. Their compound eyes each consist of up to 30,000 facets, each one dedicated to a tiny area in space. Their eyes provide them with extraordinary acuity and their shape means they have nearly 360 degree vision. While a dragonfly’s eyes are fixed, the black dot you see in the centre of their eyes represents the facets that are looking at you and as you move around the insect the size of the black dot that appears to follows you is an indication of the number and size of facets looking in your direction. Dragonflies have a fovea in which the facets are most concentrated and it is this part of the eye that they use when chasing their prey. Many dragonflies first detect their prey while sitting on a perch. After take off they quickly align their body to the trajectory of the prey and ready themselves for an attack, normally from below. The movements involved would usually cause the image of the prey object to sweep out of the fovea. However, the dragonfly compensates by rotating its head. This head rotation is nearly instantaneous with the motion of its body suggesting that most-likely the dragonfly has an on-board computer model of its prey’s movement enabling it to predict the prey’s trajectory and thus to intercept it (https://tinyurl.com/4rzs82e3). At interception, a small insect like a mosquito, is caught directly in the mouth. Larger insects, like flies, are first trapped by a dragonfly’s front legs and then shredded up by its powerful serrated jaws (mandibles). For a short while a dragonfly may fly inverted, executing a return to normal flight following a short ‘stall’ (https://tinyurl.com/mrx75ytc). You can sometimes find dragonflies perching while they finish their meals. You may be able to spot a favoured perch by virtue of the discarded wing cases and other hard parts of the insects they have captured.
Male dragonflies can be quite aggressive towards one another and will chase other dragonflies away. In these attacks, some species have been shown to use a novel form of ‘camouflage’, the attacking dragonflies adjusting their flight paths to appear stationary to their rivals, thus minimizing the chance of being detected as they approach. The attacking dragonfly flies towards his rival, choosing a line of attack such that does not deviate from the landmarks of his starting point. The target therefore does not see the attacker move from the landmark point. The only visible evidence that the attacker is moving is its looming; the change in size as the attacker approaches. Thus, though the attacker appears to get larger as he moves closer he doesn’t otherwise appear to move. Clever!
Many of the other behaviours of dragonflies are related to their need to neither overheat nor cool down too much. Despite the insistence of some of my fellow macro-photographers that there is a need to arrive on-site early in the mornings, I have found that when it is cool dragonflies tend to be hidden, perching somewhere out of sight until the morning sun can provide enough heat for their flight motors to reach critical temperature. At some point, they move to perch in the sun, sometimes shivering their wings to build up the temperature of their flight muscles. Once they are warm enough they either begin to patrol up and down seeking prey (larger dragonflies), or adopt a perch over the water where the movement of prey is obvious against the even background it provides. If scared by movement or after chasing prey, an individual dragonfly will often return to same favoured perch. On hot days, after some time flying in the sun, a dragonfly may need to cool down or risk overheating. They sometimes adopt what’s called ‘an obelisk position’. This is a sort of ‘handstand’ in which the abdomen is raised until its tip points at the sun. This minimizes the surface area exposed to solar radiation. They can also use their wing position to either gain or avoid, gaining heat. The wings can be spread toward the sun to reflect heat onto their bodies or tilted such as to minimize their exposure.
Dragon- and damsel-fly sex is complicated. The first step for the male is to approach the female from behind and grab hold of her thorax with his legs. Then, pulling his abdomen forward, he grabs her by the neck with his cerci (anal appendages). You will often see dragon- and damsel-flies flying paired in this way. The male’s penis is at the end of the abdomen but the female’s genital opening is located near her neck. Once the couple’s sex-organs are linked the bodies of the two insects form a closed circle. However, that isn’t quite it. The female of the species can mate with several males but it is only the final one that will fertilize her eggs. Special barbs on the penis of the male are used to remove sperm deposited in any earlier matings, only then will he deposit his sperm. After mating, the males of some species will simply release the female and fly away while others will hang around until she lays her eggs to guard her from mating with other males. In some species, as I have observed with Ruddy Darters, the pair will stay linked throughout the egg-laying process.
Insect migration has been studied for over 100 years. For most of that time, the Monarch Butterfly has been considered the best example of long distance migration traveling up to 2,500 miles across North America. Those butterflies living west of the Rockies travel to the Californian coast while those east of them fly south to the forests high up in the mountains of Mexico. Until recently they were thought to be the long distance travelers of the insect world. However, more recently it has been discovered that a small dragonfly Pantala flavescens, less than 4cms in length, is the real globe-trotter (https://tinyurl.com/szpx89tv). A genetic study has shown that they can journey between continents. Observations show that in four generations, they can make the journey of 18,000 kms from India to Africa. An individual Pantala is thought to be able to travel up to 6,000 kms in its lifetime and 3,500kms without stopping! Unfortunately, despite the wide distribution that has resulted from its extraordinary ability to travel long distances, they cannot cross the dry zone represented by the Sahara and thus you will not find any Pantala in Europe,. Not content with being the long-distance record holders, they also hold the record for the dragonfly found at the greatest altitude – 6,200 m in the Himalayas!
How do dragon- and damsel-flies meet their end? Well, its a dog-eat-dog world. Larger dragonfly species take many of the smaller ones. Spiders around the edges of ponds do very well and I have noticed that the larger spiders catch a lot of the medium-sized species. Birds and bats also seem to enjoy snacking on dragonflies, many of which continue to fly at twilight. Frogs and other amphibia put paid to many of the smaller species.
I am insufficiently expert to offer much advice in photographing dragonflies. What success I have had has been as a result of using a longer lens (180mm macro – full-frame equivalent – actually the 90mm OM f3,5 Pro macro lens, with or without a tele-converter), moving slowly and avoiding shadowing my prey. For some photos, I have used a flash with a diffuser for both individual photos and focus stacks. More recently, I have decided that for objects of the size and flightiness of dragonflies, you are better off using natural light even if that means pushing the ISO to 400-500. Patience is a virtue and every moment you spend pursuing dragonflies is one spent in admiration of the achievements of hundred of millions of years of evolution; beautiful and yet, deadly!
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