Northern dart moth (Xestia alpicola alpina)
| Kingdom | Animalia |
|---|---|
| Phylum | Arthropoda |
| Class | Insecta |
| Order | Lepidoptera |
| Family | Noctuidae |
| Genus | Xestia (1) |
| Size | Adult wingspan: 34-40 mm (2) Length of caterpillar: up to 35 mm (3) |
Classified as Nationally Scarce in Great Britain (4).
The form of the Northern Dart moth found in Britain (Xestia alpicola alpina), is considered to be a different race or 'subspecies' from that which occurs in mainland Europe (4). Adults are silvery grey, with blackish and reddish patches on the forewings (5). The caterpillar has wrinkled skin, is dark reddish-brown in colour with a brown head, and three pale lines and two rows of black dashes along the back (3).
The subspecies alpina occurs in parts of Scotland, the north of England and north-western Ireland (4). The main breeding areas are located in the Cairngorms, Loch Rannoch, and Cumbria (4). It has also been found on Harris and Lewis in the Outer Hebrides, the Orkney Isles, and formerly on Shetland (4).
Inhabits the higher slopes (2) and summits of mountains, typically at altitudes above 800m (4).
Although adults have been seen flying during the day, they normally fly very late at night (2). This is a single-brooded species, and adults are on the wing between late June and August (2). The eggs are laid in July, and the caterpillars emerge during the same month (3). They hide in mosses and lichens close to the foodplants (3) crowberry, ling, bilberry and bearberry, and feed on fresh young shoots (4). The caterpillars take two years to develop, overwintering twice before pupating during May (3). This species has a biennial rhythm, perhaps driven by parasitic wasps (6), so adults are typically seen only in alternate years (2).
Already limited to the tops of mountains in northern Britain, this species will have nowhere else to go if global warming affects its habitat (6).
A number of the sites supporting this moth are designated Sites of Special Scientific Interest (SSSIs) or National Nature Reserves (NNRs) (4). Furthermore, it is a priority species under the UK Biodiversity Action Plan (UK BAP); as such, a Species Action Plan has been published in order to guide its conservation. This plan aims to maintain the current range of the Northern Dart (4). In addition, English Nature has included this subspecies in its Species Recovery Programme.
Further reading on moths:
Leverton, R. (2001) Enjoying Moths. Poyser, London.
Skinner, B. (1984) Colour identification guide to moths of the British Isles. Viking, London.
Information authenticated by Roy Leverton.
- Pupation: the process of becoming a pupa, the stage of an insect's development, when huge changes occur that reorganise the larval form into the adult form. In butterflies the pupa is also called a chrysalis.
- Single-brooded: (also known as 'univoltine'). Insect life cycle that takes 12 months to be complete, and involves a single generation. The egg, larva, pupa or adult over winters as a dormant stage.
- Subspecies: a different race of a species, which is geographically separated from other populations of that species.
- National Biodiversity Network Species Dictionary (September 2002) http://www.nhm.ac.uk/nbn/
- Skinner, B. (1984) Colour identification guide to moths of the British Isles. Viking, London.
- Carter, D. J. & Hargreaves, B. (1986) Field guide to the caterpillars of butterflies and moths in Britain and Europe. William Collins Sons & Co, London.
- UK BAP Species Action Plan (September 2002): http://www.ukbap.org.uk
- Personal observation from ARKive images.
- Leverton, R. (2001) Enjoying Moths. Poyser, London