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BIODIVERSITY REFERENCE
 
   Cordulegaster boltonii (Donovan)   
 
Golden-ringed Dragonfly


Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Hexapoda
Class: Insecta
Order: Odonata – dragonflies & damselflies


British distribution: Widespread, but predominantly in the north and west; scarce or absent in much of central and eastern England and only a vagrant in Ireland.
World distribution: Europe, extending into Asia, eastern limits uncertain due to confusion with related species.


Cordulegaster boltonii
Cordulegaster boltonii female, at rest, Carmarthenshire, July 2003. Note the long ovipositor.


Cordulegaster boltonii is a true dragonfly (i.e. a member of the suborder Anisoptera, including the hawkers and darters, rather than the suborder Zygoptera, the damselflies), and is one of our largest species (wingspan 10 cm, overall length given as 84 mm in females, males slightly shorter). Like other members of the suborder, it is a strong, agile and rapid flyer and, within its size scale, a fearsome predator, taking sizeable insects on the wing, including beetles, wasps and bumblebees. Typically it patrols along streams and along the edges of other waterbodies, keeping low over the water.


Identification
It is the only British dragonfly with encircling rings of bright yellow along a black abdomen and if seen clearly it is unmistakable. However, other hawker dragonflies, notably the females of some Aeshna species, have more complex patterns of pale, yellowish spots and fine rings on a brown or dark background, and may not look very different in flight. As is typical of its suborder, the wings are spread when it is at rest and the hind wings are much broader than the fore-wings towards the base. By contrast, damselflies generally hold their wings vertically when at rest and the two pairs of wings are similar in size and shape.

There are several similar species of Cordulegaster in Europe but most are eastern and unlikely to reach Britain as vagrants. Macromia splendens is a rare and very local species of south-western Europe that also resembles C. boltonii. Distinguishing characters are given in Dijkstra & Lewington (2006).


Ecology and biodiversity assessment
As with other dragonflies, the larval (nymph) stage is aquatic, a predator in the detritus of moorland streams and pools.

Dragonflies have become a group regularly featured in biodiversity assessments. This is partly (probably substantially) because they are attractive, relatively easily identified and with not too large a number of species in Britain (42 breeding species of Odonata listed in Hammond (1985), including 3 thought to be extinct). However, they can also be considered a monitor of the overall 'health' of wetland habitats. They are sensitive to management practices, including drainage or manipulation of water levels and clearance of marginal vegetation. The nymphs require unpolluted water and agricultural runoff is a major threat. Beyond the immediate confines of waterbodies, intensive agriculture, including conversion of scrub and old meadows into 'improved' grasslands, substantially reduces the availability of insect prey. It follows that a rich dragonfly and damselfly fauna is a sign of a high grade site. It should be noted, however, that many species are southern in their British distribution, irrespective of availability of apparently suitable habitat, Cordulegaster boltonii being unusual in being more northern and to a substantial extent seeming directly to replace some of the Aeshna species.


References
Modern, well illustrated, information and identification guides to British species include:
•   Brooks, S., & Lewington, R. (2002). Field guide to the dragonflies and damselflies of Great Britain and Ireland, 3rd ed., British Wildlife Publishing, Hook.
•   Corbet, P.S., & Brooks, S.J. (2008). Dragonflies, Collins New Naturalist, London.
•   Dijkstra, K.-D.B., & Lewington, R. (2006). Field guide to the dragonflies of Britain and Europe including western Turkey and north-western Africa, British Wildlife Publishing, Milton on Stour.
•   Hammond, C.O. (1985). The dragonflies of Great Britain and Ireland, updated version of 2nd edition (revised by R.Merritt), Harley Books, Colchester.
•   McGeeney, A. (1986). A complete guide to British dragonflies, Jonathan Cape, London.
•   Smallshire, D., & Swash, A. (2004). Britain's dragonflies. A guide to the identification of the damselflies and dragonflies of Great Britain and Ireland, WILDGuides Ltd., Old Basing.



© A.J. Silverside
Page first hosted at www-biol.paisley.ac.uk/bioref/, September 2003, December 2008; transferred to lastdragon.org with minor edits, November 2009
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