Forge Valley – Yorkshire Dragonfly Group

Beautiful Demoiselle Calopteryx virgo

Posted on 26 April 2009 by Paul Ashton

Length

45-49mm; Wingspan: Male 58mm; Female 63mm; Hindwing 24-36mm; Larva: 30-35mm

Male

Dark brown-black wings, with iridescent blue veins making the wings appear metallic cobalt blue. Extreme tips and bases may be paler, there is no pterostigma. Wings are broader than the similar Banded Demoiselle. Body is metallic blue-green. Immatures wings are browner.

Female

Dark brown iridescent wings with a white ‘false pterostigma’, larger on forewing than hindwing. Wings are browner than the similar Banded Demoiselle. Body is metallic green with a bronze tip to abdomen. Homeochrome, (male coloured females) are sometimes recorded.

Behavior

Territorial males perch on bankside vegetation. They will flick their wings open and shut, occasionally chasing off passing insects, often returning to same perch. Females only visit water for egg-laying or seeking a mate, both sexes frequently stray well away from water. Flies slowly with a butterfly like flight and frequently settles on bankside vegetation or trees.

Habitat

Restricted to faster running clear water, found only along streams and rivers, often acidic, with sand or gravel bottom. Mostly found along heathland or moorland streams, though can also occur in farmland and woodland, including well shaded streams. Prefers cooler water than Banded Demoiselle. As streams broaden this species gives way to Banded Demoiselle, where there may be a broad overlap. Occasional hybridisation may take place. Sensitive to waterway management (clearance of vegetation) and pollution.

Flight Period

Status

VC61 – Only finds its way into the Vice-county due to the new course of the River Hertford being cut south of the old North and East Riding County Boundary. In many places this is within metres of the boundary.
VC62 – Extremely localised to the south-eastern area of the North Yorkshire Moors.

Distribution Map

Locations

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Banded Demoiselle Calopteryx splendens

Posted on 26 April 2008 by Paul Ashton

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Length

45-48mm; Wingspan: Male 61mm; Female 65mm; Hindwing 27-36mm; Larva: 30-40mm

Males

Translucent wings with a broad, dark iridescent blue-black band on outer part of both wings, there is no pterostigma. Body is metallic blue-green. Immatures wing band is dark brown.

Females

Translucent pale green wings, white ‘false pterostigma’, larger on forewing than hindwing, metallic green body. Sometimes androchrome females are observed (male coloured females), these can be identified by the ‘false pterostigma’ which males lack.

Behavior

Males are territorial, though large numbers can be found together. They attract females by flicking their wings open whilst performing an aerial dance in front of them, flopping down on to the egg-laying site. Females stay away from water unless looking for a mate or egg-laying. Adults will make use of nettle beds and tall grasses to rest.

Habitat

Mature, slow-flowing streams, rivers and canals, with muddy sediment. Can overlap with Beautiful Demoiselle where habitat contains patches of sand and gravel. Prefers open banksides, where as Beautiful Demoiselle will happily use shady areas. Adults of both sexes can be found well away from water and ponds where breeding is unlikely, thought they will breed in lakes adjacent to rivers. Sensitive to waterway management (clearance of vegetation) and pollution.

Flight Period

Status

Abundant along occupied rivers and streams.

Distribution Map

Locations

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Southern Hawker Aeshna cyanea

Posted on 22 April 1995 by Paul Ashton

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Length

70mm, Wings 98mm.

Males

Thorax – green and brown with broad green antehumeral stripes; abdomen – yellow triangle segment 2, green spots segments 3-8; undivided blue spots segments 9-10; wings brownish tinge; legs brown-black.

Females

Thorax – green and brown with broad green antehumeral stripes; abdomen brown with green spots, undivided green spots on segments 9-10.

Habitat

Lakes and ponds, including small garden ponds where it is the most likely Aeshnidae to be encountered. Also found along canals and ditches. Will feed away from breeding sites, sometimes being encountered in sheltered areas, such as woodland rides and hedgerows.

Behavior

Males are territorial, with a single male usually found at a small pond. There is however a constant change of males throughout the day. This is an inquisitive species, often approaching close to the observer. They can be active in dull weather, often on the wing late into the evening, even hunting when it is raining. Copulation takes place away from water, lasting for around two hours. The female oviposits into waterside vegetation, moss or bare soil above water, often in poor weather. Larvae emerge after two to three years on tall marginal vegetation. They mature away from water over a four to six week period, before returning to suitable sites to breed.

Flight Period

Distribution Map

Locations

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Four-spotted Chaser Libellula quadrimaculata

Posted on 22 April 1986 by Paul Ashton

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Length

43mm, Wings 76mm

Males

Thorax brown, no antehumeral stripes; abdomen brown, last 4 segments darker than the rest, yellow spots on sides; wings dark patches at nodes on leading edges and at bases of rear wings.

Females

Similar to males, main difference is the shape of the anal appendages.

Habitat

Prefers sites of still water consisting of lakes, ponds, bog pools, canals and dykes. Will tolerate brackish conditions. The largest concentrations are associated with acidic ponds and pools.

Behavior

Males are territorial, their noisy clashes are obvious where densities are high. Readily returns to the same perch on emergent vegetation, after sparring with other males, or after short patrols along the waters edge. Copulation is short taking place in flight, only lasting for 5-20 seconds. Female oviposits by flicking the abdomen tip downwards into the water. The eggs then sink and adhere to submerged vegetation. Males may stay close by to guard females during oviposition. Larvae live among the bottom debris, then emerge after two to four years. Emergence takes place amongst marginal vegetation during daylight hours.

Flight Period

Distribution Map

Locations

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