Insects - Dragonflies

Image above by John Walters
Southern damselfly Coenagrion mercuriale - Endangered and nationally rare

This dainty damselfly is declining throughout its European range. Although its two main British strongholds are in the New Forest and the Preseli mountains, Pembrokeshire, the colonies in East Devon and on Dartmoor are considered of international significance. This species has specialised habitat requirements, being confined in Devon to shallow, well-vegetated, base-rich runnels and flushes. There are seven extant colonies in the county, including one satellite (Lower Prewley), of which four are on Dartmoor and three are on the East Devon Pebblebed Heaths (EDPH). Transects at all sites are monitored annually for adults, while the Dartmoor sites are checked for larvae in spring. Three sites have experienced substantial increases in numbers following the introduction of positive management during the last 25 years. The trends for six sites are currently judged to be stable, apart from one EDPH site (Colaton Raleigh Common), where numbers have crashed to single figures for the last four years; the reasons for this are unclear but may be related to the cessation of water loss from a leaking pipe. Two sites in the Blackdown Hills, Southey Moor and Hense Moor, were last occupied in 1959 and 1965, respectively; a recent translocation attempt at the latter appears to have failed. However, extinction in 1991 at one EDPH site, Venn Ottery Common Devon Wildlife Trust Reserve, was followed by targeted management and successful re-establishment using New Forest stock in 2007 and 2009.

Map to show the Devon distribution of this species

Further Sources of information:

Devon Dragonfly Group

British Dragonfly Society