The Scarce Chaser occurs on just a few river systems in England so the Sussex population is important. Among British species, the male has a unique combination of a black-tipped, powder-blue abdomen, and dark patches at the base of the wings. Maturing females have a velvety ginger appearance, with a distinct smoky patch at the tip of each wing and a saffron streak along their upper edge. As they age they go a drab brown.
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Scarce Chaser adult male Photo: Simon Linington
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Scarce Chaser immature male Photo: David Sadler
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Scarce Chaser young male Photo: Simon Linington
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Scarce Chaser immature female Photo: David Sadler
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Freshly emerged Scarce Chaser and exuvia Photo: David Sadler
National status
Restricted to about ten river systems [6 main localities - BDS website] and nearby still waters in southern and eastern England. Populations appear to be stable and there is some evidence that the species may be extending its range. Listed under category 3 (scarce) in the British Red Data Book on Insects.
Status in Sussex
The Dragonflies of Sussex (2004) states that it is “Confined to West Sussex, although there have been very occasional sightings in East Sussex. Its range is largely confined to the River Arun, from Billingshurst to Amberley, where it can occur in large numbers. There are a few records for the western Rother, where it meets the Arun and a few sporadic sightings on the Adur tributaries.” Since then, its distribution has expanded eastwards into East Sussex with well-established populations along the Rivers Ouse and Cuckmere. There have also been scattered gains along the Arun and Adur. Listed in the Sussex Rare Species Inventory.
Distribution at 1km scale
Historical records
According to Lucas and Bloomfield (1905) and later authors the first record seems to have been by Unwin on the Lewes Downs and reported by him in The Naturalist of July 1853. Although observed by G. Furley at Midhurst in 1924, it was not until 1937 that J. Cowley recorded it at its present stronghold on the Arun (Chelmick 1979).
Flight times
Early May - mid July.
Phenology (adult)
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Scarce Chaser habitat at Barcombe Mills Photo: Simon Linington
Habitat
Slow-moving rivers with water meadows, occasionally gravel pits and ponds. It has a preference for sunny, sheltered spots, with plenty of vegetation, avoiding areas of heavy shade.
Conservation
Throughout its British range the Scarce Chaser is vulnerable to river pollution, and inappropriate river management and improvement schemes. Concern about the species is not new. Cynthia Longfield (1937) wrote that “it should be very carefully preserved where it does breed”. Recent decades have seen a significant conversion from traditional wet grazing meadows to drained arable fields, in Sussex as elsewhere. This change of habitat, alongside pollution from fertilisers and pesticides, has adversely affected the Scarce Chaser, even though the River Arun itself is nominally protected by its status as a Site of Special Scientific Interest. We need to improve our understanding of the species’ ecological requirements. The BDS also quotes over-shading, changing water levels and excessive boat traffic as potential threats.
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Similar species Males. Similar species that all have blue abdomens and more-or-less of medium dragonfly size are the Broad-bodied Chaser, the Black-tailed Skimmer and the Keeled Skimmer. Separating them is relatively easy. Scarce Chasers and Keeled Skimmers have bluish eyes, Black-tailed Skimmers have green ones and Broad-bodied Chasers have brown ones. Both Scarce Chaser and Broad-bodied Chaser have black patches at the base of the wings (small and large, respectively) whereas the two skimmers have no patches. Scarce Chasers uniquely can have smoky patches on the wing tips though these are not always obvious or present. Scarce Chasers and Black-tailed Skimmers have noticeable dark tips to the abdomen; the other two don’t. The Broad-bodied Chaser has a very broad abdomen with noticeable yellow patches on the side. The Black-tailed Skimmer has a yellow leading edge to the wing (costa).
Females. In addition to the species mentioned above, isolated females must be distinguished from Four-spotted Chasers. The latter are brown, rather stocky dragonflies and can quickly be identified by the four dark spots on each pair of wings. The patches on the wings noted for the males holds true for the females. Female Broad-bodied Chasers have the same broad abdomens of the males. Female (and immature male) Scarce Chasers are unmistakable with their orange abdomen and a dark, jagged line running down its length. The female (and immature male) Black-tailed Skimmers have a rather yellowish abdomen strongly marked with black that creates the impression of a rather triangular abdominal cross-section. Fortunately, Keeled Skimmer normally can be ruled out in all but certain heathland locations. Unlike the other three species it has yellowish (rather than dark) wing spots (or pterostigma).
A further useful identification pointer is that Chasers nearly always perch on vegetation whereas Skimmers favour the ground.
The Scarce Chaser occurs on just a few river systems in England so the Sussex population is important. Among British species, the male has a unique combination of a black-tipped, powder-blue abdomen, and dark patches at the base of the wings. Maturing females have a velvety ginger appearance, with a distinct smoky patch at the tip of each wing and a saffron streak along their upper edge. As they age they go a drab brown.
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Scarce Chaser adult male Photo: Simon Linington
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Scarce Chaser immature male Photo: David Sadler
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Scarce Chaser young male Photo: Simon Linington
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Scarce Chaser immature female Photo: David Sadler
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Freshly emerged Scarce Chaser and exuvia Photo: David Sadler
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Scarce Chasers mating Photo: David Sadler
National status
Restricted to about ten river systems [6 main localities - BDS website] and nearby still waters in southern and eastern England. Populations appear to be stable and there is some evidence that the species may be extending its range. Listed under category 3 (scarce) in the British Red Data Book on Insects.
Status in Sussex
The Dragonflies of Sussex (2004) states that it is “Confined to West Sussex, although there have been very occasional sightings in East Sussex. Its range is largely confined to the River Arun, from Billingshurst to Amberley, where it can occur in large numbers. There are a few records for the western Rother, where it meets the Arun and a few sporadic sightings on the Adur tributaries.” Since then, its distribution has expanded eastwards into East Sussex with well-established populations along the Rivers Ouse and Cuckmere. There have also been scattered gains along the Arun and Adur. Listed in the Sussex Rare Species Inventory.
Distribution at 1km scale
Historical records
According to Lucas and Bloomfield (1905) and later authors the first record seems to have been by Unwin on the Lewes Downs and reported by him in The Naturalist of July 1853. Although observed by G. Furley at Midhurst in 1924, it was not until 1937 that J. Cowley recorded it at its present stronghold on the Arun (Chelmick 1979).
Flight times
Early May - mid July.
Phenology (adult)
1 / 1
Scarce Chaser habitat at Barcombe Mills Photo: Simon Linington
Habitat
Slow-moving rivers with water meadows, occasionally gravel pits and ponds. It has a preference for sunny, sheltered spots, with plenty of vegetation, avoiding areas of heavy shade.
Conservation
Throughout its British range the Scarce Chaser is vulnerable to river pollution, and inappropriate river management and improvement schemes. Concern about the species is not new. Cynthia Longfield (1937) wrote that “it should be very carefully preserved where it does breed”. Recent decades have seen a significant conversion from traditional wet grazing meadows to drained arable fields, in Sussex as elsewhere. This change of habitat, alongside pollution from fertilisers and pesticides, has adversely affected the Scarce Chaser, even though the River Arun itself is nominally protected by its status as a Site of Special Scientific Interest. We need to improve our understanding of the species’ ecological requirements. The BDS also quotes over-shading, changing water levels and excessive boat traffic as potential threats.
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Photos: Simon Linington & David Sadler
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Photos: David Sadler & Simon Linington
Similar species Males. Similar species that all have blue abdomens and more-or-less of medium dragonfly size are the Broad-bodied Chaser, the Black-tailed Skimmer and the Keeled Skimmer. Separating them is relatively easy. Scarce Chasers and Keeled Skimmers have bluish eyes, Black-tailed Skimmers have green ones and Broad-bodied Chasers have brown ones. Both Scarce Chaser and Broad-bodied Chaser have black patches at the base of the wings (small and large, respectively) whereas the two skimmers have no patches. Scarce Chasers uniquely can have smoky patches on the wing tips though these are not always obvious or present. Scarce Chasers and Black-tailed Skimmers have noticeable dark tips to the abdomen; the other two don’t. The Broad-bodied Chaser has a very broad abdomen with noticeable yellow patches on the side. The Black-tailed Skimmer has a yellow leading edge to the wing (costa).
Females. In addition to the species mentioned above, isolated females must be distinguished from Four-spotted Chasers. The latter are brown, rather stocky dragonflies and can quickly be identified by the four dark spots on each pair of wings. The patches on the wings noted for the males holds true for the females. Female Broad-bodied Chasers have the same broad abdomens of the males. Female (and immature male) Scarce Chasers are unmistakable with their orange abdomen and a dark, jagged line running down its length. The female (and immature male) Black-tailed Skimmers have a rather yellowish abdomen strongly marked with black that creates the impression of a rather triangular abdominal cross-section. Fortunately, Keeled Skimmer normally can be ruled out in all but certain heathland locations. Unlike the other three species it has yellowish (rather than dark) wing spots (or pterostigma).
A further useful identification pointer is that Chasers nearly always perch on vegetation whereas Skimmers favour the ground.
