Methods for identifying dragonflies (2024)

Collecting and Identifying Dragonflies

The identification of dragonflies, as in any other field of natural history, depends on a combination of careful observation and experience of the species in the field. Becoming confident and expert in dragonfly identification takes patience and time. A thorough knowledge of the common species is needed, and once gained the unusual and rare species will be more easily found. It is recommended that males should be learnt first. In most species the males are the most conspicuous and most often encountered sex especially amongst the damselflies. The different behaviour of females mean they tend to be much less conspicuous. Lone females can often be difficult to identify, but where males are present, females can be more easily identified by observing how the males react to their presence.

Fieldcraft and Equipment

You can look at dragonflies without any equipment. Dragonflies can be seen and appreciated by sitting quietly beside water in sunny weather. It can be worth slowly approaching perched insects for a closer look. This is much easier (but less pleasant!) when the weather is dull. Cooler temperatures on dull cloudy days or in the evening make dragonflies less active and reluctant or unable to fly. The damselflies in particular have the habit of dropping deep into vegetation if disturbed when the air temperature is low. They can then be surprisingly difficult to find!

Good weather is essential for pleasant and productive fieldwork and, in Ireland, this essentially means sunny, warm days. Dull, sunless days can be very unproductive especially when combined with wind and rain. Some of the most productive days are those with the first good weather after some poor conditions. For instance a bright sunny afternoon after a dull, wet morning. Windy weather makes dragonflies difficult to observe and keep track of, and in these conditions dragonflies should be looked for in sheltered situations such as along hedgerows or on the edge of woods.

Whilst damselflies are relatively easy to observe, the larger dragonflies and anything over water present more of a challenge. To cope with these a net or a pair of binoculars is essential equipment. Which you prefer to use will come down to personal preference. If using binoculars choose a pair that are close-focussing.

To correctly identify some species or even just to get a close look to fully appreciate the adults insects, a net is an indispensable tool. Carrying an insect net does not signify anything sinister and if used properly does the insect no harm. To use a net does require some practice but when this is gained it becomes the best way of catching and identifying the species. Even apparently slow-flying damselflies can be very difficult to keep under observation. It also has to be recognised that for some species netting and observation in the hand is required for positive identification. This is especially true for female damselflies and we have indicated in the species pages where particular problems can arise.

Types of nets

There are many types of net available and what you end up using will be determined by personal choice. Heavy duty pond and sweep nets are not suitable. What is needed is a insect net with a lightweight nylon bag and an aluminium handle. Nets can be either black or white. Some species are reported to detect and avoid white nets, so black is often recommended, but technique is probably as important for success. Nets should have wide openings (30cm diameter is typical) and the bags should be at least as deep as wide. The frame can be round or kite-shaped. A large opening is an advantage for catching larger species, but this has to be balanced against portability and manoeuvrability. A long and preferably extendable handle is needed. We personally use circular nets with a diameter of about 30cm, with a deep black nylon bag. The net handle is 70cm long but telescopic so it can be doubled in length.

Techniques

• If used carefully nets will not cause damage to mature, adult dragonflies.
• Newly emerged (teneral) adults should not be netted or handled. These can be recognised by their shiny wings and the lack of pigmentation.
• Avoid catching too many specimens at once
• Do not use nets when wet - they become heavier and are more likely to cause damage to the insects.
• Damselflies can be caught be general stalking and sweeping whilst they are perched or in flight.
• Dragonflies are best caught by swinging the net rapidly up and from behind the insect, but be prepared for many misses!
• To stop the insect escaping flick the net so that the bag closes over the opening.
• Extract the insect by grasping the wings at the base and gently closing them between finger and thumb.
• The insect will not damage itself if held in this way, and can be released by placing it on a suitable perch and just releasing the wings.

Net suppliers

B & S Entomological Services, 37 Derrycarne Road, Portadown, BT62 1PT, Co. Armagh, Northern Ireland (028 3833 6922).

GB Nets (pond nets only), 45 Burnley Road, Todmorden, Lancs OL14 7BU (Tel: 01706 813941).

Watkins & Doncaster, PO Box 5, Cranbrook, Kent TN18 5EZ (Tel: 01580 753133).

Confirmation of identification

The collecting of adult insects can be a contentious issue in these days of concern for conservation. Collecting of adult dragonflies has never been a common practice as the colours which make them so attractive in life, fade rapidly after death. As dragonflies are also easy to identify in the field the taking of specimens is rarely justified. However specimens can have a use in teaching identification allowing the relative size and features of individual species to be compared with others. Specimens can also be used as vouchers to support a record. However the taking of large numbers of adults cannot be condoned as it serves no purpose. One stage of the dragonfly lifecycle - the exuvia, the shed larval skin - can be collected with impunity. It does no harm to the species and additionally the finding of exuvia at a site proves that the species has emerged from it. The exuvia retains the form and features of the larvae and can be identified in the same way. Studies of the exuvia and emergence behaviour is a productive field and one which has been neglected in Ireland. So why not give it a go! If collecting exuviae record details such as habitat, emergence position, distance from breeding site and plant species as well as the date and usual details. exuviae look fragile but can persist for some time after emergence. They are best examined wet and stored tubes of 70% alcohol.

To get expert confirmation of identification for adults they should be photographed or drawn and notes made to highlight the important features.

Nelson, B., Thompson, R. & Morrow, C., 2000 (September 12). [In] DragonflyIreland http://www.ulstermuseum.org.uk/dragonflyireland/

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