Treeton Dyke – Yorkshire Dragonfly Group

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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Emerald Damselfly Lestes sponsa

Posted on 22 April 2007 by Paul Ashton

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Length

35-39mm; Wingspan: Male 42mm; Female 45mm; Hindwing 19-22mm

Male

Metallic green in colour. This species has a slow maturation period of two to four weeks, over this period a blue pruinescence appears on the thorax between wings and segments 1,2, 9 and 10. Eyes blue. Confusion species is Scarce Emerald Damselfly which is extinct in Yorkshire. Both sexes rest with wings half open.

Female

Metallic green, with pale beige sides to the thorax. Distinctly thicker abdomen than male.

Behaviour

Weak flyer usually remaining close to emergent vegetation, rarely going far over water. Copulation usually takes place close to breeding site and last from 30 minutes to over an hour. Females usually arrive to oviposit in tandem with the male. Oviposits in to stems of emergent grasses, rushes, sedges and horsetails, usually above surface, but can submerge, including the male. Fairly sedentary and can be absent from seemingly good sites.

Habitat

Still or slow moving water such as ponds, bogs, ditches, canals and lake edges with dense emergent vegetation. Tolerates brackish and acidic water. Sensitive to excessive clearance of emergent vegetation.

Flight Period

Status

Found at many sites through all Vice-counties.

Distribution Map

Locations

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Red-eyed Damselfly Erythromma najas

Posted on 22 April 2004 by Paul Ashton

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Length

33-37mm; Wingspan: Male 43mm; Female 46mm; Hindwing 19-24mm

Male

Mainly bronzed black with bright red eyes. Top of thorax lacking any antehumeral stripes. Segments 1, 9 and 10 are blue. Sides of thorax are blue with black line and spur present. Legs are black. Immature male is similar to female. Similar to Small Red-eyed Damselfly which is smaller, differences occur in the blue markings. At rest the wing tips reach in to segment eight, in Small Red-eyed Damselfly the wing tips only reach as far as segment 6 or 7. Generally holds its abdomen level, where as Small Red-eyed Damselfly often holds its abdomen slightly upcurved towards the end.

Female

Mainly black with green sides to thorax containing black line and spur. Segments 9 and 10 are black with narrow blue divisions. Eyes are a dull red colour. Usually have short shoulder stripes, though some lack them all together and some may form as explanation marks.

Behaviour

Strong direct flight over water. Spend lots of time resting on broad floating leaves such as water lilies. Mats of algae and debris are also used and males may use surrounding shrubs if there is little floating vegetation. After emergence they will spend time away from water to mature. The first three weeks of emergence is probably the best time to encounter this species at close quarters. Females usually only appear at water to breed. Copulation takes place over water or on nearby vegetation. Egg laying is mainly in tandem, both sexes often submerging. They are laid mainly on the underside of Water Lilies, though other floating vegetation will be used.

Habitat

Preference for larger ponds, lakes and canals. Requires abundant floating vegetation, such as water-lilies Nymphaceae, or broad-leaved pondweed Potamogeton natans. When these are absent it may use floating algae mats, or rest on bankside vegetation.

Flight Period

Status

Species is at the northern edge of its range in Yorkshire.

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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Common Blue Damselfly Enallagma cyathigerum

Posted on 22 April 1999 by Paul Ashton

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Length

32mm, Wings 36-42mm

Male

Bright blue body with black markings on upper surface of abdomen, segment 2 has lollipop mark; segment 8 and 9 all blue; broad antehumeral stripes on black thorax; eye spot linked by bar.

Female

3 colour forms:-
1) abdomen with black markings.
2) Green with black markings.
3) Brown with black markings. All have characteristic medial spine under segment 8, presumably puncturing plant material before inserting an egg.

Habitat

Large ponds and lakes are the main preference for this species. Can also be found along canals and rivers, but will also tolerate brackish conditions. The most abundant Zygoptera found in open areas.

Behavior

The most dominant species on large lakes and reservoirs, swarming over the waters surface far from the banks in sunny conditions. Readily settles on emergent vegetation and is aggressive towards others, even driving away larger species. Copulation lasts for around 20 minutes, frequently away from water. Oviposits into submerged and emergent vegetation, usually in tandem. If the female submerges the male will uncouple, guarding the area waiting for her to re-emerge. Females can submerge for up to an hour. Larvae live amongst submerged vegetation emerging after 1-3 years. They mature in surrounding areas over a period of around 12 days.

Flight Period

Status

Occurs on a wide range of varying water-bodies. Can be more conspicuous than the similar Azure Damselfly. Blue damselflies ranging far over open water are usually this species. Generally the most abundant blue damselfly at sites, where the Azure can be absent.

Distribution Map

Locations

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Migrant Hawker Aeshna mixta

Posted on 22 April 1996 by Paul Ashton

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Length

63mm, Wings 87mm

Males

Thorax brown with broad thoracic stripes, with short indistinct antehumeral stripes; abdomen brown, yellow triangle mark on segment 2, separate pairs of blue spots along rest of abdomen; legs brown; eyes bluish; wings have brown costa.

Females

Thorax antehumeral stripes very restricted, often missing; abdomen brown with small yellow-brown spots; long anal appendages. Brown costa, leading edge to the wing.

Habitat

Still or slow-flowing waters including ponds, lakes, sand and gravel pits, reservoirs, slow-flowing rivers, canals and ditches. Will tolerate brackish conditions, though avoids acidic water.

Behavior

None territorial and often present in high densities with little sign of aggression. Frequently hovers, searching for females in marginal vegetation. Both sexes can be found well away from water in sheltered locations, such as woodland rides and hedgerows. Regularly found perched in the open. Copulation is lengthy and once complete, the female will oviposit alone. Oviposition usually occurs into emergent plants above the water, though occasionally in bare mud. Emergence usually occurs the following year, often during the night. Despite being abundant late in the season, few exuviae have been found. Those that have been recovered are usually found low down in thick vegetation. Due to the lack of breeding data, it would suggest that the majority of adults observed are migratory individuals.

Flight Period

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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Brown Hawker Aeshna grandis

Posted on 22 April 1994 by Paul Ashton

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Length

73mm, Wings 102mm.

Males

Thorax brown; abdomen brown with bright blue spots at sides; wings characteristically honey brown colour; legs pale brown.

Females

As males except blue spots on abdomen replaced with yellow markings.

Habitat

Lakes, ponds, gravel pits, canals, ditches and slow-flowing rivers. Will tolerate moderate levels of pollution.

Behavior

Males are territorial, even defending territories away from water. They are often observed hawking along woodland rides and hedgerows. This is a difficult species to approach when settled, the first sign of their presence is usually the rustling of wings, as the fly up from roosting places in tall grasses. Copulation is lengthy, the female then ovipositing into emergent floating vegetation, or decaying floating logs, where several females may oviposit together. Larvae emerge two to four years later at night, with the maiden flight taking place before dawn.

Flight Period

Distribution Map

Locations

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Emperor Dragonfly Anax imperator

Posted on 22 April 1992 by Paul Ashton

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Length

78mm Wings, 106mm.

Males

Thorax bright green; abdomen blue with black central line; legs black; eyes green; wings clear with yellow costa.

Females

Generally greenish with thicker black central abdominal line.

Habitat

Ponds, lakes, gravel pits, dykes, canals and slow-flowing rivers with rich marginal vegetation, also tolerant of brackish conditions. Seldom found far away from water.

Behavior

Males are territorial, rarely more than one male is present at small locations. Constantly patrols its territory, which it defends vigorously. Will take prey as large as Four-spotted Chaser Libellula quadrimaculata. Copulation takes place away from water and lasts around ten minutes. The female then oviposits alone into submerged vegetation. Larvae emerge after two years on to tall emergent vegetation. Emergence is usually synchronous at site level.

Flight Period

Distribution Map

Locations

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