DAMSELFLIES & DRAGONFLIES

G.D. Lewis (with reference to S. Jones 1997 extract)

The 40 species of Odonata resident in Britain are divided into two sub-orders, the Zygoptera (Damselflies) with ten breeding species present in Cornwall, and the Anisoptera (Dragonflies) of which thirteen are known to breed in the Duchy. Populations of resident species are frequently joined by migrants from continental Europe; these include Red-veined Darter Sympetrum fonscolombei and, more rarely, Yellow-winged Darter Sympetrum flaveolum and Vagrant Emperor Hemianax ephippiger. As reported in the 1997 edition of this publication, Cornwall has probably seen both the Southern Damselfly Coenagrion mercuriale and the Orange-spotted Emerald Oxygastra curtisii become extinct; there have been no confirmed records of either species in the last ten years. The legacy of the Cornish mining industry, both tin and china clay, is a key source of prime habitat for the species group. Sites which contain the greatest diversity of species are, with few exceptions, those which have been shaped by the mining effort. Good examples of prime ex-mining habitat are the Red River Valley, near Camborne, and the China Clay workings based around St. Austell. Cornwall hosts three nationally scarce species of Damselfly, two of which benefit from the residue of the mining industry: the Scarce Blue-tailed Damselfly Ischnura pumilio favours sites where vegetation is slow to re-colonise and the Small Red Damselfly Ceriagrion tenellum prospers on old mining sites where acid boggy pools have developed. The other nationally scarce damselfly found in Cornwall, the White-legged Damselfly Platycnemis pennipes, is only found around the River Tamar and its tributaries, whilst Cornwall’s only nationally scarce dragonfly, the Black Darter Sympetrum danae, is almost exclusively found around the boggy pools on Bodmin Moor. Whilst common throughout much of southern England, the Black-tailed Skimmer Orthetrum cancellatum is locally scarce in Cornwall and relies heavily on shallow serpentine quarries on the Lizard Peninsula and china clay workings around St. Austell, although its range has increased during the last ten years. Since the last publication of Red Data Book for Cornwall and the Isles of Scilly, the Lesser Emperor Anax parthnope has partially established itself as a breeding species in east Cornwall at a newly developed complex of fishing lakes. This site has also become a regular site for Red-veined Darter. The British Dragonfly Society has undertaken work to update the “Key Sites” project initially begun in the early 1990s. Each county has a set of criteria that identifies a key site and for Cornwall that means a site that supports a breeding population of one or more of the following: Scarce Blue-tailed Damselfly, Small Red Damselfly and Ruddy Darter Sympetrum sanguineum. In 1993, Cornwall had 53 such sites; this has increased to 71 in 1999. No rare or nationally scarce dragonflies occur in the Isles of Scilly. Only three species breed in the islands, Blue-tailed Damselfly Ishnura elegans, Common Darter Sympetrum striolatum and recently Migrant Hawker Aeshna mixta. As in mainland Cornwall a number of species occur as vagrants without becoming established. Perhaps the most unusual being several individuals of an North American species the Green Darner Anax junius that turned up in 1998. The 1km grid square data comes from the National Dragonfly Recording Scheme records available on the NBN Gateway for the period post 1997. The following species are those which are deemed to have local status; it includes the nationally scarce species, locally scarce breeding species and notes on the two species deemed to have become extinct. One species, Migrant Hawker Aeshna mixta has increased significantly since 1997 in a number of sites and it has been removed from the species given RDB status.

Platycnemis pennipes White-legged Damselfly

Ceriagrion tenellum Small Red Damselfly

Coenagrion mercuriale Southern Damselfly

Ischnura pumilio Scarce Blue-tailed Damselfly

Erythromma najas Red-eyed Damselfly

Anax parthenope Lesser Emperor

Oxygastra curtisii Orange-spotted Emerald

Orthetrum cancellatum Black-tailed Skimmer

Sympetrum fonscolombii Red-veined Darter

Sympetrum sanguineum Ruddy Darter