Value as Bio-indicators
Dragonflies and Damselflies can be used as bio-indicators of water quality and freshwater habitat quality. They typically spend 1 to 2 years of their lives as aquatic nymphs, require good water quality to survive to adulthood, and can react quickly to changes in environmental quality.
Dragonfly and damselfly nymphs are commonly used as bio-indicators of water quality, using kick-sampling techniques. However in-water sampling is not desirable from a citizen science perspective.
Luckily, adult dragonflies and damselflies are readily available for visual survey without getting your feet wet! They are also reasonably easy to identify to species level. With a bit of caution, adult dragonflies and damselflies can also be used to assess water quality and freshwater habitat quality.
Some species, such as the Emperor Dragonfly, can also be used as bio-indicators of climate change as they expand their range to the north in response to increasing average temperatures.
Surveying Dragonflies & Damselflies
Surveys should be carried out on dry, sunny, cloudless, and windless days. Ideally the temperature should be above 17oC, though for Irish conditions, 15oC is the recommended minimum . Often surveys during the first sunny weather after a prolonged period of poor weather can be most productive. As it takes a while for dragonflies and damselflies to warm up and get active, it is generally recommended to survey between 10AM and 4PM.
Dragonflies and damselflies may be observed without the aid of any equipment. Just wait until the animal perches on some low vegetation and approach slowly and carefully. This task is often easier in dull, cooler weather. To observe more distant animals or those on the wing over water, a pair of close-focusing binoculars may be used.
For those with more than a passing interest in dragonflies and damselflies, a net is a worthwhile investment. An insect net made of black lightweight nylon is best. Nets with a telescopic aluminium handle may prove useful. Ensure that your net has sufficient depth to allow the net to close over the entrance by flipping the handle.
Never attempt to net newly emerged adults (tenerals) as they are too delicate. Tenerals may be recognised by their shiny wings and lack of colour. Never use a wet net as it may damage the insects.
Damselflies may be netted by sweeping when the animals are perched or in flight. Dragonflies are best netted by sweeping up and from behind the animal.
Grasp the insect at the base of the wings, gently closing them between finger and thumb. This will not hurt them an you can release by placing on a suitable perch and letting go.
The best times to photograph dragonflies and damselflies are early morning and late afternoon when temperatures are below those required for flight. Chasing after highly active animals during the hotter parts of the day generally does not yield good results, though some success may be had with a good zoom lens. Days of mixed cloud and sun can be productive as animals settle while the clouds pass over, don’t forget to leave them settle for a few minutes before trying to approach to take a photo. Searching low lying branches and shrubs near to breeding pools can also yield results.
Where numbers of animals are low, direct counts for each species may be attempted. Where numbers are higher, estimating according to count codes may be more realistic e.g. A=1, B=2-5, C=6-20 etc… In mixed species groups or damselfly or dragonfly, the total count for each species may be extrapolated by catching and identifying a representative sample (e.g. 10%) of the animals.
Identifying Dragonflies & Damselflies
Boys & Girls
Males and females of dragonfly and damselfly species may differ markedly. Generally, it is best to focus on males initially for identification purposes as they are more colourful and more clearly marked. When surveying, males are more likely to be found closer to the water and therefore it is recommended to focus your search within 2m of the water’s edge (where it is safe to do so), and 5m over the surface of the water (visually).
Females tend to have more drab colours and are more easily confused with other species. The further you are from the water’s edge, the more less likely you will find males and more likely you will find females.
Exuviae & Tenerals
Exuviae are the larval casings left behind by newly emerged adult dragonflies and damselflies. The exuviae retain the larval form and can be identified to species. They are generally found on vegetation at the water’s edge but can be difficult to locate. Exuviae are best stored wet in 70% alcohol for identification purposes.
Tenerals are the recently emerged adults. They tend to have shiny wings and are lacking the colour of the mature adults. Tenerals are also far more delicate than the mature adults and should never be handled or netted.
Surveying Dragonflies & Damselflies
|Common Name||Species Name|
|Golden-ringed Dragonfly||Cordulegaster boltonii|
|Hairy Dragonfly||Brachytron pratense|
|Common Hawker||Aeshna juncea|
|Brown Hawker||Aeshna grandis|
|Migrant Hawker||Aeshna mixta|
|Emperor Dragonfly||Anax imperator|
|Lesser Emperor||Anax parthenope|
|Vagrant Emperor||Hemianax ephippiger|
|Downy Emerald||Cordulia aenea|
|Northern Emerald||Somatochlora arctica|
|Four-spotted Chaser||Libellula quadrimaculata|
|Keeled Skimmer||Orthetrum coerulescens|
|Black-tailed Skimmer||Orthetrum cancellatum|
|Common Darter||Sympetrum striolatum|
|Red-veined Darter||Sympetrum fonscolombii|
|Ruddy Darter||Sympetrum sanguineum|
|Black Darter||Sympetrum danae|