We distinguish here between capturing a dragonfly (retaining the option of releasing it promptly) and collecting a dragonfly (with the intention of killing and preserving a specimen for future study). This distinction applies to adults and larvae.
It may be necessary to capture a dragonfly in order to examine it closely (e.g. to identify it, or to estimate its degree of maturity) with the prospect of releasing it promptly. Unnecessary capture should always be avoided because sometimes an adult can be fatally injured during the process. This applies especially but not exclusively to large, swiftly flying species. To capture them a net may have to be swung with force and speed. If the rim of the net strikes the dragonfly’s head the impact can damage the delicate head-arrester system (p.212) in the neck and so destroy the dragonfly’s ability to manoeuvre in flight. Such damage will be fatal. Likewise marking should not be practised except for good cause because it sometimes reduces survivorship, especially if the marks are conspicuous, perhaps making the dragonfly more visible to predators.1
Existing books and manuals on Odonata contain ample guidelines for techniques and equipment, but in any case keen practitioners will soon learn from experience by noting the habits of fliers and perchers and by learning to avoid alerting a settled dragonfly by making a sudden movement or casting a shadow over it. It has recently been shown that adults of some stream-dwelling species (e.g. Cordulegastridae) are attracted visually to a rotating object such as a small electric fan.2 It may not be necessary to kill a dragonfly if all that is needed is a sample for DNA analysis; a small part of a leg may suffice.
To capture larvae one needs an inflexible, long-handled, sturdy net with a quick-drying bag (nylon is suitable), a mesh size of about 1 x 1 mm and a rigid triangular frame that allows the net to penetrate dense stands of aquatic plants. The contents of a sweep can be tipped into water in a shallow white tray for inspection. The mesh size of the net can be varied according to the bottom sediment and to the need to collect small larvae. Larvae that live in silt, leaf litter or peat can be collected effectively using a sieve. Larvae of all sizes usually reveal themselves by their movements and can be taken out of the sorting tray to be placed in holding containers, using a suction pipette (for small larvae) or fingers or forceps (for larger ones), and isolated to avoid predation. Some kinds of weed-dwelling larvae can be collected using a submerged trap (Fig. 71, p.142). After being isolated, each larva may have to be examined and measured individually in a small, translucent dish under a dissecting microscope.
It is encouraging to know that F-o exuviae (left behind at the emergence site) (p.149) can, at least for Anisoptera, be determined reliably to species3 and so can serve as voucher specimens. They have the added advantage that they provide unequivocal evidence of successful breeding. Also they are a reliable source of DNA for genetic analysis.4
During an investigation it may be necessary to retain a specimen to be preserved for dissection or microscopic examination. Such a specimen is termed a voucher specimen or voucher. The consensus among odonatologists, at least those who are members of the Worldwide Dragonfly Association (WDA), is that collecting dragonflies should comply with four key principles. These form the basis of the Code of Practice for Collecting promulgated by the Association (see Box A.1).5 This is the most comprehensive and practical code known to us and we recommend that it be adhered to by all odonatologists.
WDA CODE OF PRACTICE FOR COLLECTING DRAGONFLIES
Principle 1. To respect life, in the form of species, communities and habitats.
1.1. Unless needed for education or scientific research, no larval or adult dragonfly should be killed, either as a sequel to capture or through habitat destruction. Of these two types of intervention, the second is by far the more serious as a threat to the continuity of dragonfly populations.
1.2. Live dragonflies should only be held captive for good scientific reasons, under conditions that do not expose them to avoidable stress, and for no longer than necessary.
1.3. Specimens of dragonflies that have been collected should not be offered for sale.
1.4. Recognising that sometimes scientific study will require a series of specimens to be secured, no more specimens should be collected than are needed. The collector should always exercise discrimination and restraint and proceed in a spirit consistent with the principles espoused in the Code.
1.5. The habitat in which specimens are being collected should be damaged as little as possible.
1.6. Specimens of one species should not be collected in large numbers from the same locality in the same season.
Principle 2. To comply with existing regulations.
2.1. Before any dragonfly is collected, or collected material exported from its country of origin, all existing, relevant regulations, including the common law of the country, should have been complied with. Such regulations may include permission to enter land, to collect certain species, to collect biological material of any kind, and to export or retain it. It is recognised that an unexpected encounter may sometimes require an odonatologist to secure, and perhaps retain, a dragonfly without having obtained the requisite permission beforehand. In such an event, it is assumed that, if the specimen is collected in a place where restrictions are known to apply (e.g. a nature reserve), the appropriate authorities will be informed soon afterwards.
2.2. When the collecting site is a nature reserve or a site of known interest to conservationists, a list of species collected should be supplied in due course to the owner or managing authority, whether or not to do so is a requirement when permission is granted.
Principle 3. To respect the need for scientific rigour.
3.1 Sometimes larval or adult dragonflies have to be collected and preserved as voucher specimens in order to further odonatology through education and scientific research, including the validation of scientific identity. Sound taxonomy is central to odonatology and sound taxonomy almost invariably depends on the existence of properly annotated material. All voucher specimens should be adequately preserved and labelled, and thereafter properly curated. Where feasible, and in due course, they should be deposited in a suitable museum or institution or, if retained in a private working collection, their whereabouts should be made known to odonatologists generally.
Principle 4. To show, and expect to receive, tolerance of differing attitudes towards collecting biological material.
4.1. If a WDA member who is collecting in compliance with this Code encounters overt disapproval from anyone at the collecting site, that member should respond to that disapproval by explaining the need for voucher material and by citing the authority that legitimises the action of trying to obtain it.
4.2. It is recommended that WDA members conduct their activities in a manner consistent with this Code, and, at their discretion, report to the WDA Board any activity inconsistent with the Code. WDA unequivocally endorses the need to collect voucher specimens of dragonflies for the furtherance of odonatology through scientific research. WDA unequivocally deplores the behaviour of anyone who tries to obstruct, intimidate or slander anyone trying to collect dragonflies while complying with this WDA Code of Practice.
[Version of February 2002, revised October 2004.]
Settled dragonflies make rewarding subjects for colour photography. Guidelines for appropriate equipment and procedures are given by Robert Thompson and Dagmar Hilfert-Rüppell and Georg Rüppell.6 An exciting, recent development has been the use of the auto-focus device which, coupled with a digital camera, makes it possible to take repeated images of a flying dragonfly at little cost, thus greatly increasing the likelihood of obtaining a crisp image of a dragonfly in flight.7 Several of the plates in this book, taken by Steve Cham, are products of this innovative approach.
It is a fundamental tenet of the scientific method, including odonatology, that opportunity should exist for observations to be verified by an independent investigator. Sometimes this is possible only if vouchers are available for scrutiny, a need addressed by clause 3.1 in the WDA Code. Fortunately it is not always necessary that a voucher be retained in order to be confident of a diagnosis. Sometimes the use of close-focus binoculars or a photograph may suffice, or the close examination of an adult specimen in the hand, preferably using a magnifying glass and a modern field guide, for example when distinguishing species of Erythromma, Lestes and some species of Coenagrionidae. However, there are other instances when a voucher will need to be retained, as the following examples illustrate. Anax ephippiger and A. parthenope, two aeshnids that sometimes visit Britain, resemble each other in flight and are extremely difficult to photograph. In the absence of vouchers, we suspect that British records of A. ephippiger, which were fairly frequent before the 1990s, may represent A. parthenope. Since A. parthenope was first recorded in Britain (in 1996) there have been few (if any) substantiated records of A. ephippiger but regular (annual) records of A. parthenope. Another, confirmed example of the need for a voucher is the specimen of an adult Sympetrum from Dawlish, Devon, originally identified (by an experienced odonatologist) as S. meridionale, but much later found to be S. striolatum.8 Sometimes exotic Odonata appear in Britain, probably having been imported as eggs on water weeds flown in to Britain for the aquarist trade.9 One such species is the widespread Palaearctic and tropical libellulid Crocothemis servilia. We know of no way of reliably distinguishing this species from the Eurasian C. erythraea without recourse to a powerful magnifying glass or a microscope.10 Yet C. erythraea is now being reported from Britain,11 often without vouchers being retained to enable identifications to be checked. In 1998 the North American aeshnid, Anax junius, known as the Green Darner, an habitual migrant in the New World, was sighted several times in Cornwall and the Isles of Scilly, but no vouchers were retained.12 So The Natural History Museum, London, was deprived of a specimen. This was especially unfortunate, partly because this was the first recorded case of a transatlantic passage by a North American dragonfly, and partly because the external diagnostic characters of this species are very variable, sometimes closely resembling those of Anax imperator.13 Indeed it appears that A. junius may have reached Europe before the first recorded sighting in September 1998: in 1989 an undated observation was reported of a species of Anax (recorded as A. imperator) ovipositing in tandem near the Atlantic coast of France.14 Such behaviour is rarely or never exhibited by A. imperator, but is commonplace in A. junius. Again no voucher was retained. In retrospect it seems highly likely that the tandem pair seen on that occasion was A. junius,15 but of course we shall never know!
We recognise that opinions differ regarding the propriety of collecting dragonflies. However, there is no doubt that the interests of odonatology and nature conservation sometimes require that a voucher be secured and retained. Odonatology will suffer serious and lasting damage unless this fact is acknowledged, with a good grace, by people who prefer not to collect dragonflies. If and when conflicts arise there is a consensus among active odonatologists (and ornithologists) that the way forward must be through civilised dialogue based on mutual understanding and respect for differing points of view.12 It would be tragic if unity of purpose among odonatologists and conservationists were to be jeopardised by a failure to acknowledge the imperatives of good science. We believe that the WDA Code offers sound guidelines for achieving the necessary compromise and understanding. In the few notorious cases when an odonatologist has been obstructed or abused for trying to secure a voucher12 such behaviour has been denounced by some institutions that feel responsible for the conduct of their members.16
We are left with three conclusions:
1) sometimes a voucher must be secured;
2) in such a case the decision to secure a voucher must be made by an experienced odonatologist who should stand ready to explain on request why a voucher is needed; and
3) any attempt to obstruct or abuse an odonatologist trying to secure a voucher should be denounced publicly and promptly by institutions responsible for the integrity and conduct of the relevant branches of science.
Although we unreservedly endorse the principle that dragonflies (and other animals) should never be killed needlessly, we think it appropriate to emphasise (when the collection of vouchers is at issue) that, in general, populations of dragonflies are extremely unlikely to be endangered by the removal of one or two individuals. This is partly because populations are often deceptively large: David Thompson was surprised to discover that at two fen sites the annual population of adult Coenagrion mercuriale was close to 40,000 individuals, peaking at 5,000 to 6,000 a day;17 also, as mentioned in the WDA Code (clause 1.1), the most severe and widespread threat to dragonfly populations results from habitat destruction caused by human activities. The latter is best constrained by habitat conservation for which a biological survey (which often requires vouchers) is a sine qua non.
One final point should be made. Anyone obtaining a voucher should be mindful of clause 3.1 of the WDA Code which stipulates that a voucher should be deposited in a place which is made known and where it can be available for scrutiny by other investigators. So collectors need to make appropriate arrangements. An obvious depository will always be an entomological museum, but this may not always be feasible in future as such museums reach their limits for further acquisitions. If the collector retains a voucher in a private working collection, the collection’s contents and whereabouts should be made known through conventional channels.
When a faunistic or ecological survey is being undertaken and in other cases when an accurate identification of a dragonfly is essential, the retention of a voucher should be the rule and not (as now) the exception. Organisations dispensing grants for research and biodiversity surveys should be aware of this requirement. Under the auspices of the Biological Survey of Canada (Terrestrial Arthropods) comprehensive guidelines have been published for obtaining vouchers, and attention drawn to the pitfalls of failing to do so, when conducting systematic, faunistic and ecological research.18