Norfolk Hawker
Encyclopedia
Aeshna isoceles is a small hawker dragonfly
that is found in Europe
, mostly around the Mediterranean, and the lowlands of North Africa
. Its common name in English is Green-eyed Hawker. In Britain
it is a rare and local species and is known as the Norfolk Hawker. It has a brown colour with green eyes and clear wings and also a yellow triangular mark on the second abdominal segment which gave rise to its scientific name. It used to be in the genus Anaciaeschna
as it has several differences from the other members of the Aeshna
genus. Its specific name is often spelt isosceles.
and around the Mediterranean and, the lowlands of North Africa
. It is more common in eastern Europe than the south western Europe; it occurs in Spain
and Portugal
but is local.
It is found wet areas, ponds, ditches and marshes, with dense vegetation and, in studies carried out in England, was found to be associated with Water-soldier (Stratiotes aloides).
fen
s but by the early 1980s the populations had greatly declined. It is now confined to relatively unpolluted fens and grazing marshes in the Broadlands of Norfolk
and north-east Suffolk
. It can be found in Hickling Broad
and two National Nature Reserve
s: Mid-Yare NNR
and Ludham - Potter Heigham NNR
. It is protected under Schedule 5 of the Wildlife and Countryside Act 1981
and listed in Category 1 (endangered
) in the British Red Data Books on Insects.
It is one of the earliest Aeshna
dragonflies to be on the wing with a flight period from May to August. Adults do not spend as much time on the wing as other Aeshnas. Males will fly around over a stretch of water defending a territory and if the pond is small the male will hover over the centre of the pond. Unlike other aeshnas, where the adults seem to be continuously on the wing beating up and down their territory, male A. isoceles come to rest on vegetation from time to time. Females oviposit
onto plants and the eggs hatch in about 2 weeks. Larval development takes 2 years.
and in many books is called Aeshna isosceles: however the original specific name was isoceles. Dijkstra and Lewington (2006) and Boudot JP., et al.. (2009) both call it Aeshna isoceles whereas Askew, R.R. (2004),and earlier books, refer to it as Aeshna isosceles.
Dragonfly
A dragonfly is a winged insect belonging to the order Odonata, the suborder Epiprocta or, in the strict sense, the infraorder Anisoptera . It is characterized by large multifaceted eyes, two pairs of strong transparent wings, and an elongated body...
that is found in Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
, mostly around the Mediterranean, and the lowlands of North Africa
North Africa
North Africa or Northern Africa is the northernmost region of the African continent, linked by the Sahara to Sub-Saharan Africa. Geopolitically, the United Nations definition of Northern Africa includes eight countries or territories; Algeria, Egypt, Libya, Morocco, South Sudan, Sudan, Tunisia, and...
. Its common name in English is Green-eyed Hawker. In Britain
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
it is a rare and local species and is known as the Norfolk Hawker. It has a brown colour with green eyes and clear wings and also a yellow triangular mark on the second abdominal segment which gave rise to its scientific name. It used to be in the genus Anaciaeschna
Anaciaeschna
Anaciaeschna is a genus of dragonflies in the family Aeshnidae.The genus contains the following species:*Anaciaeschna donaldi *Anaciaeschna isosceles - Green-eyed Hawker, Norfolk Hawker...
as it has several differences from the other members of the Aeshna
Aeshna
Aeshna is the scientific name of a genus of dragonflies from the family Aeshnidae. They are also known as hawker dragonflies, or, in North America, as mosaic darners.-Description:These are relatively large dragonflies...
genus. Its specific name is often spelt isosceles.
Identification
A. isoceles is one of only two brown hawkers found in Europe, the other is A. grandis. Both have a brown thorax and abdomen but A. isoceles has green eyes and clear wings and a diagnostic yellow triangular mark on the second abdominal segment. The hindwings have an amber patch at their base. In contrast A. grandis has yellowish wings and blueish eyes. The green eye of A. isoceles stand out even in flight and in practice it is not difficult to tell these two dragonflies apart. In addition to the morphological differences A. isoceles is on the wing much earlier in the year than A. grandis.Distribution and habitat
A. isoceles is found in central EuropeEurope
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
and around the Mediterranean and, the lowlands of North Africa
North Africa
North Africa or Northern Africa is the northernmost region of the African continent, linked by the Sahara to Sub-Saharan Africa. Geopolitically, the United Nations definition of Northern Africa includes eight countries or territories; Algeria, Egypt, Libya, Morocco, South Sudan, Sudan, Tunisia, and...
. It is more common in eastern Europe than the south western Europe; it occurs in Spain
Spain
Spain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...
and Portugal
Portugal
Portugal , officially the Portuguese Republic is a country situated in southwestern Europe on the Iberian Peninsula. Portugal is the westernmost country of Europe, and is bordered by the Atlantic Ocean to the West and South and by Spain to the North and East. The Atlantic archipelagos of the...
but is local.
It is found wet areas, ponds, ditches and marshes, with dense vegetation and, in studies carried out in England, was found to be associated with Water-soldier (Stratiotes aloides).
Status in Britain
The Norfolk Hawker has always been a scarce and local insect in Britain. It used to be found in the CambridgeshireCambridgeshire
Cambridgeshire is a county in England, bordering Lincolnshire to the north, Norfolk to the northeast, Suffolk to the east, Essex and Hertfordshire to the south, and Bedfordshire and Northamptonshire to the west...
fen
Fen
A fen is a type of wetland fed by mineral-rich surface water or groundwater. Fens are characterised by their water chemistry, which is neutral or alkaline, with relatively high dissolved mineral levels but few other plant nutrients...
s but by the early 1980s the populations had greatly declined. It is now confined to relatively unpolluted fens and grazing marshes in the Broadlands of Norfolk
Norfolk
Norfolk is a low-lying county in the East of England. It has borders with Lincolnshire to the west, Cambridgeshire to the west and southwest and Suffolk to the south. Its northern and eastern boundaries are the North Sea coast and to the north-west the county is bordered by The Wash. The county...
and north-east Suffolk
Suffolk
Suffolk is a non-metropolitan county of historic origin in East Anglia, England. It has borders with Norfolk to the north, Cambridgeshire to the west and Essex to the south. The North Sea lies to the east...
. It can be found in Hickling Broad
Hickling Broad
Hickling Broad lies within The Broads National Park in Norfolk, England,. 4 km south-east of Stalham.It is a National Nature Reserve established by English Nature and in the care of the Norfolk Wildlife Trust, who run boat trips around the reserve for visitors. It is also part of the Upper...
and two National Nature Reserve
National Nature Reserve
For details of National nature reserves in the United Kingdom see:*National Nature Reserves in England*National Nature Reserves in Northern Ireland*National Nature Reserves in Scotland*National Nature Reserves in Wales...
s: Mid-Yare NNR
Mid-Yare NNR
Mid-Yare NNR is a National Nature Reserve in Norfolk, east of Norwich, established by English Nature and managed by the Royal Society for the Protection of Birds . In RSPB publications, this reserve is known as Strumpshaw Fen....
and Ludham - Potter Heigham NNR
Ludham - Potter Heigham NNR
Ludham–Potter Heigham Marshes NNR is a National Nature Reserve established and owned by English Nature in Norfolk, England. Located within The Broads National Park, it is an internationally important wetland site....
. It is protected under Schedule 5 of the Wildlife and Countryside Act 1981
Wildlife and Countryside Act 1981
The Wildlife and Countryside Act 1981 is an Act of Parliament in the United Kingdom and was implemented to comply with the Directive 2009/147/EC on the conservation of wild birds...
and listed in Category 1 (endangered
Endangered species
An endangered species is a population of organisms which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters...
) in the British Red Data Books on Insects.
Behaviour
Aeshna
Aeshna is the scientific name of a genus of dragonflies from the family Aeshnidae. They are also known as hawker dragonflies, or, in North America, as mosaic darners.-Description:These are relatively large dragonflies...
dragonflies to be on the wing with a flight period from May to August. Adults do not spend as much time on the wing as other Aeshnas. Males will fly around over a stretch of water defending a territory and if the pond is small the male will hover over the centre of the pond. Unlike other aeshnas, where the adults seem to be continuously on the wing beating up and down their territory, male A. isoceles come to rest on vegetation from time to time. Females oviposit
Oviposition
Oviposition is the process of laying eggs by oviparous animals.Some arthropods, for example, lay their eggs with an organ called the ovipositor.Fish , amphibians, reptiles, birds and monetremata also lay eggs....
onto plants and the eggs hatch in about 2 weeks. Larval development takes 2 years.
Systematics
This species was first described as Libellula quadrifasciata, var. 36. isoceles by Muller in 1764. It has since been called Aeshna rufescens and Aeshna chysophthalmus and more recently Anaciaeschna isosceles. It is by this last name that it is referred to in many books. It has since been included into the genus AeshnaAeshna
Aeshna is the scientific name of a genus of dragonflies from the family Aeshnidae. They are also known as hawker dragonflies, or, in North America, as mosaic darners.-Description:These are relatively large dragonflies...
and in many books is called Aeshna isosceles: however the original specific name was isoceles. Dijkstra and Lewington (2006) and Boudot JP., et al.. (2009) both call it Aeshna isoceles whereas Askew, R.R. (2004),and earlier books, refer to it as Aeshna isosceles.