Guidelines for the Selection of Biological Heritage Sites
7. Section 2: Species Guidelines
7.8 INVERTEBRATES: DRAGONFLIES AND DAMSELFLIES (ODONATA)
Application (all invertebrate guidelines)
Identification of sites on the basis of their invertebrate animal species should take account of the needs of many invertebrates for habitat and structural diversity, both at the 'macro' and 'micro' scales. Small-scale habitats of particular importance to some invertebrates, such as dead wood or small patches of bare ground, occur and indeed may shift their position over time within large scale habitats e.g. woodland or grassland, on which the invertebrates also depend. Moreover the larval and adult phases of the same species often need quite different habitats. Invertebrates generally have annual life cycles, and their survival on a site depends on the continued availability of the right mixture of habitats at the right time of year - every year. Such factors should be taken into account when determining site boundaries.
Species lists, especially for less well-recorded groups of invertebrates, should be regarded as tentative. They include species recorded in Lancashire since 1950, those not recorded since 1978 being shown with an asterisk, or other notation.
It should be noted that the category 'nationally scarce', referring to species believed to occur between 16 and 100 10km squares of the National Grid, is sometimes subdivided in relation to invertebrate groups into 'Notable A' and 'Notable B'. This subdivision has not been recognised in the following guidelines.
Justification
In Lancashire, as elsewhere, there are more species of invertebrate animals than of all plants and other animals combined. Many invertebrate groups and species have declined dramatically in recent decades, and their conservation is a matter of widespread concern in Europe. Until recently, it was thought that if sites were selected (and managed) on the basis of their botanical interest, then the invertebrates would automatically be catered for too. This is not so: it is important that due regard is paid to the contribution that invertebrates make to biodiversity, and of their habitat needs, in their own right, insofar as available information allows.
With such a large number of invertebrate groups, and the relative lack of knowledge about many of these, it is impossible to develop individual sets of guidelines for every species-group at the present time. Where there is an adequate database for a particular species-group relating to Lancashire, specific guidelines have been devised and appear below. For the remainder, there is a single, 'catch all', section which follows the standard approach adopted throughout the species section.
ii) DRAGONFLIES AND DAMSELFLIES (ODONATA)
Application (all dragonfly and damselfly guidelines)
For the purposes of these guidelines, acceptable evidence of breeding by dragonfly and damselfly species includes a female seen ovipositing, or the identification of larvae or the identification of exuvia. Wherever possible, the most recent record of breeding should be within 3 years of the site selection date.
When defining site boundaries, adjacent semi-natural terrestrial habitat, including night-perching habitat, should be included, according to the known requirements of the species present. Sites may include more than one water body (including ponds, ditches, streams and rivers) where they are linked by suitable habitat.
Justification (all dragonfly and damselfly guidelines)
Dragonflies are a conspicuous and popular group which have been relatively well-recorded in recent years. All species have aquatic larvae which spend from 1 to 3 years in water. The abundance of these species is to some extent a useful indicator of the state of the aquatic environment generally: small lakes and large lowland ponds usually support the greatest diversity of species.
Od1 Any site which regularly supports a breeding population of a species of dragonfly or damselfly included in British Red Data Books: 2. Insects(1).
Application
There are presently no Lancashire records for the species to which this guideline relates.
Justification
The species in the above category are either threatened or rare in Britain and there is a national responsibility for their conservation.
Od2 Any site which regularly supports a breeding population of a 'nationally scarce' species of dragonfly or damselfly.
Application
The species to which this guideline applies include:
| Sympetrum sanguineum | Ruddy Darter |
Justification
Nationally scarce species are recorded only from 16-100 10km squares (inclusive) in Britain; their conservation is a matter of national concern.
Od3 Any site which regularly supports a breeding population of a species of dragonfly or damselfly which occurs at 3 or fewer sites in Lancashire.
Application
Any site for species in this category which are not covered by Guidelines Od1 or Od2 may be considered for inclusion although the distribution of the Broad-bodied Chaser may be expanding and should be kept under review. The species to which this guideline applies include:
| Calyopteryx splendens | Banded Demoiselle |
| Libellula depressa | Broad-bodied Chaser |
Justification
Many dragonfly species are highly mobile, and some are presently expanding their ranges in Britain.
These are species which, although common in some parts of England, are rare in Lancashire. Subject to further localities being colonised or discovered, they may provisionally be regarded as 'endangered' in a County context.
Od4 Any site which regularly supports a breeding population of a species of dragonfly or damselfly which is recorded from more than 3 localities in Lancashire, but which could be at risk because of small populations, habitat loss or change, or is at the edge of its British range, where such populations contribute significantly to the distribution pattern or the total population size of that species in the County.
Application
Sites for species in the above categories (not included under Guidelines Od1 or Od2) may be considered for inclusion where they significantly extend the geographical range of the species in Lancashire, or support a significant proportion of the estimated total County population of that species.
The species to which this guideline relates include:
| Anax imperator | Emperor Dragonfly |
| Cordulegaster boltonii | Golden-ringed Dragonfly |
| Lestes sponsa | Emerald Damselfly |
| Libellula quadrimaculata | Four-spotted Chaser |
| Sympetrum danae | Black Darter |
Justification
Species included here, whilst not as rare in Lancashire as those under Guideline Od3, are nevertheless either of very restricted distribution, or exist only as small scattered populations, in the County
Od5 Any site which regularly supports breeding populations of 7 or more species of dragonfly or damselfly.
Application
Any site which satisfies this guideline should be included. The following species are relevant for the purposes of this guideline:
| Aeshna cyanea | Southern Hawker |
| Aeshna grandis | Brown Hawker |
| Aeshna juncea | Common Hawker |
| Anax imperator | Emperor Dragonfly |
| Coenagrion puella | Azure Damselfly |
| Cordulegaster boltonii | Golden-ringed Dragonfly |
| Enallagma cyathigerum | Common Blue Damselfly |
| Ischnura elegans | Blue-tailed Damselfly |
| Lestes sponsa | Emerald Damselfly |
| Libellula quadrimaculata | Four-spotted Chaser |
| Pyrrhosoma nymphula | Large Red Damselfly |
| Sympetrum danae | Black Darter |
| Sympetrum striolatum | Common Darter |
Justification
The purpose of this guideline is to identify sites with high structural and habitat diversity which support notable assemblages of dragonflies and damselflies.
(1) Shirt (1987)