River Hertford – 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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Blue-tailed Damselfly Ischnura elegans

Posted on 22 April 2002 by Paul Ashton

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Length

29-34mm; Wingspan: 35-40mm; Hindwing 14-21mm

Male

Dark bronze-black metallic with blue segment 8. Blue or green sides to the thorax and antehumeral stripes. Blue eye spots. Pterostigma is distinctive being bi-coloured black and white. Tips of the lower appendages diverge.

Female

Occur in several colour forms dependent on age. Segment 8, though not always blue, is usually clearly different from the other sections. Start as either rufescens with a reddish-pink thorax and blue segment 8 or violacea with a violet thorax and antehumeral stripes, black humeral stripes and blue segment 8. After around eight days they mature and change colour, rufescens become greenish-brown of the form rufescens-obsoleta. The form violacea mature into two separate from. The first is infuscans which is a pale green colour, and retaining the black humeral stripes. The second is an andromorph form which adopts the same colours as a male.

Behavior

Often found in marginal vegetation in large numbers. Copulation last from between two to six hours, due to this, it is the most frequently observed species seen in the wheel position. Often females selected by the males are still in their immature colour forms. Females oviposit alone onto the tissue of aquatic plants and debris, where they are not usually harassed by the males. Frequently found in dull weather when other species are inactive. Larvae emerge after one to two years.

Habitat

Wide range including garden ponds, lakes, rivers, canals and ditches. Can also be found in brackish conditions and acidic peaty pools. More tolerant of pollution than other species, only really avoiding fast-flowing water. Readily disperses and is one of the first species to colonise new sites.

Flight Period

Status

Common and widespread throughout the area.

Distribution Map

Locations

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Azure Damselfly Coenagrion puella

Posted on 22 April 2001 by Paul Ashton

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Length

33mm, Wings 36-44mm

Males

Bright blue body with black markings; thorax black top with 2 thin antehumeral stripes; abdomen black U-shaped mark segment 2, segment 8 blue and 9 marked black; eyes bright spots not joined by a bar.

Females

2 colour forms:-
1) Body green with black markings on upper surface; segment 2 with black thistle shape.
2) Blue form has “mercury” shape on segment 2; rest of black upper markings are more extensive; narrow pale antehumeral stripes.

Note: The shape of the pronotum is the only conclusive way to seperate this species from Variable Damselfly. Personal observations have highlighted that female Azure Damselflies lack the bar between the eye spots, compared to Variable Damselfly.

Comments

Initially this species is more abundant than the similar Common Blue Damselfly with which it can be easily confused. It is easy to make the mistake of identifying early blue damselflies as being Azure, then assuming on later visits that this is still the case. However after four of five weeks, Azure can suddenly become harder to find as Common Blue Damselfly become more abundant.

Habitat

Wide range of habitats from garden ponds, lakes, ditches, streams, canals and rivers to peaty pools. The main requirement is plenty of marginal vegetation in sheltered locations. Frequently settles on floating vegetation, as well as being readily found in adjacent grasslands and sheltered woodland edges.

Behavior

Not territorial. Copulation is prolonged on warm sunny days. Pairs oviposit in tandem into soft plant tissue, often submerging to do so. Larvae live among submerged vegetation and emerge after one year. Emergence takes place on marginal vegetation or flower spikes in the centre of water bodies. Females emerge first, followed a few days later by the males.

Flight Period

Status

Common

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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