By Sally Westwood
I visited the slow flowing stream that runs parallel to the river Deben, on several occasions during the summer, looking for dragonflies. This is my first season of observing and photographing dragonflies and damselflies. I would like to share with you, my field notes. In my last article I discussed damselflies observed in the same location. My focus now turns to dragonflies. My knowledge and learning was obtained from observation, then I researched aspects of behaviour that I saw, such as mating and egg laying behaviour. The most interesting observations of the dragonflies were the different ovipositing behaviour (laying of eggs), which could be alone or together with mate, and different locations for both mating, and ovipositing. I came across four dragonflies on the riverbank: The Emperor; Southern Hawker; Migrant Hawker, and Common Darter.
Emperor Dragonfly
I observed a fairly large dragonfly laying eggs in June. It was an Emperor (Anax imperator) dragonfly. The Emperor dragonfly is the largest species of dragonfly in the UK. It has an average length of 78mm and average wingspan of 106mm. This species has a mating and flight season between June and August (see the chart below of the flight and mating period of the dragonflies discussed here).
Emperor Dragonfly Ovipositing
The female was laying eggs by curving her abdomen around in a right angle, towards the water and inserting eggs into floating vegetation in the centre of the stream. The angle of her abdomen was a signal to any male emperor dragonflies that she does not wish to mate. This species frequents large weedy canals, lakes, and ponds, rather than streams, however this stream did have extensive areas of weed. It was also edged with reeds, brambles, and hawthorn, and a wood was on the opposite side of the stream. A wood is vital for Emperor dragonflies since they mate in treetops, rather than perched on foliage, like other dragonflies, such as the Common Darter (Sympetrum striolatum). After mating, the female Emperor immediately lays her eggs by dropping her eggs into vegetation, as above. The eggs and larva over-winter before emerging as adults from their larva in June.
Timings of the Emergence, Adulthood and Mating in the four Dragonflies
Source: Sally Westwood
Key: Dark blue/red – peak mating; Light blue/red – flight season; Red – migrant (Migrant Hawker), Blue – resident dragonflies
Southern Hawker
In July, I spotted the larva of a Southern Hawker (Anshna Cyanea), (see image below). The larva is the stage before a young dragonfly reaches adulthood. The dragonfly has a three stage development,
Larva of a Southern Hawker
from an egg, to larva, and finally to an adult dragonfly. As you can see, the casing is the general shape of the emerging dragonfly, for example, it shows some of the 10 segments of the abdomen. In the image, the larva casing is split open, and the dragonfly is slowly emerging. The dragonfly has to wait for their wings to expand and harden, for up to two hours. The first flight occurs after about 2-3 hours. It feeds up away from water for up to 5 weeks and then returns to the water to look for a female. The image below shows the new Southern Hawker that emerged from the larva, waiting for its wings to be ready for flight.
Newly Emerged Southern Hawker
The Southern Hawker is a large dragonfly. It has an average length of 70mm and average wingspan of 100mm, but it is still 6mm shorter in length of the Emperor dragonfly, and has a 6mm smaller wingspan than the Emperor. This gives an indication of the remarkable size of the Emperor dragonfly. It’s mating and flight season is between July and September (see chart below of the flight and mating periods of the dragonflies discussed here)1. The male, as in the image above, is yellow, apple green and blue and brown on the abdomen (see my sketch of dragonfly glossary below). He has a green and yellow head. The frons shows a ‘t’ shape attached to a thin line. This can be seen in the image. His eyes are brown and blue-green. You can just see an eye in the compound eye structure. The thorax is brown with light green sides, beneath the wings and shows two dark brown stripes. His legs are black-dark brown. I can only make out two long, pointed, leaf shaped claspers at the end of the abdomen, I cannot see a lower clasper which is described as shorter than the other two, and is a triangle shape. I cannot see the pterostigma on the wings of the male, however, it is red and gradually turns dark brown. The female is mostly apple green with a yellow head and green eyes. The hindwing is angular in the male, but the female has more rounded wings.
Similarly to the Emperor dragonfly the Southern hawker mates in the tree tops. The female immediately flies alone to rotting wood, submerged vegetation, or rocks at the edge of water. Like the female Emperor, she rushes round rustling through foliage inserting eggs into the wood, the vegetation and on the rocks, she also uses a curved ovipositor to push out her eggs.
In September, I saw a female Southern Hawker laying eggs in amongst the foliage, rather than the centre of the stream, like the female Emperor. She flew along the edge of the water on her own laying her eggs on large stones or damp pieces of wood. I was alerted to her presence by the sound of rustling wings as she flew through vegetation. This raises the question, is it only large dragonflies that lay their eggs alone. I have not managed to find an answer to that question.
Dragonfly Glossary
Migrant Hawker
In September, I observed a pair of Migrant Hawkers (Anshan mixta) mating, unlike the Emperor and the Southern Hawker dragonflies, they were perched on a reed stem, fully visible, and although distant, were accessible for a photograph.
Pair of Migrant Hawkers Mating
The Migrant Hawker is smaller than the Emperor and Southern Hawker. It is 63mm in length and has a wingspan of 85mm. However, it still looks like a large dragonfly when observed in the field.
It’s mating and flight season is between June to late October (see chart above of the flight and mating periods of the Migrant Hawker)2. The male, at the top of the image above, has a dark brown background on his abdomen (see glossary above), with large sky blue spots. His thorax is brown and we can see two light green stripes on each side. His clypeus and fons are yellow-green, with a black ‘t’ shape on the top, visible in the image. He has blue compound eyes, facing forward in the image. The female has a similar pattern on the abdomen, but has a lighter brown background, with light green spots. The latter look yellow in the image.
The status of the term “migrant” in the dragonflies’s name, is not really applicable for all Migrant Hawkers. Some Migrant Hawkers arrive here from Europe between June and August to mate and lay eggs, but they do not live long enough to return abroad. They only live about 4-8 weeks as an adult. It is rare for those dragonflies that emerge here to fly south3 (see the chart above of the flight period of the Migrant Hawker). The short adult stage contrasts greatly with the larvae stage. The eggs diapause, they wait for the right month to emerge because of cold environmental conditions, before hatching into larvae. The larvae lives underwater amongst the weeds from one to two years. It feeds on small fish, not usually larger than itself4. This process of change occurs in all dragonflies. However, the migration itself remains a mystery. Migrant Hawkers have been caught in bird nets at a bird observatory in Estonia, suggesting autumn migration along the Baltic coastline. However, the regularity of that migration remains unknown6. There has only been evidence of Migrant Hawkers flying along with a northerly tail wind and heading north, presumably for the UK7.
Later in September I saw a female Migrant Hawker laying eggs alone, in the same manner as the female Emperor and the Southern Hawker. Her abdomen was curved round and down into water, amongst the reeds and she was depositing eggs. She was rustling about in the undergrowth but I could not see her clearly enough for a photograph.
Common Darter
I frequently came across Common Darters near the stream. They have a behavioural routine that consisted of perching for awhile, watching out for flies, flying after flies, and landing back on the same perch or one close by to eat the fly.
In September I observed a pair of Common Darters flying in tandem, with a male at the front, using his claspers or anal appendages (see my dragonfly glossary below) to grasp the female’s head and force her to lay her eggs over water (see image below). The pair bob up and down, rapidly, making a completely sharp image of both dragonflies impossible, hence the out of focus male at the front of the tandem. Each time the female touches the water she inserts the end of her abdomen into water, she releases eggs and they are flushed away. Common Darters have a mating and flight season between June and October, although it can continue later into the season (see chart above of the
Common Darters in Tandem Ovipositing
flight and mating periods of this species). The Common Darter is found all over England and wales but not Scotland. It is considerably smaller than the Emperor and the hawker dragonflies.
Male Common Darter
The Common Darter has an average length of 37mm and average wingspan of 58mm. It is half the size of the Southern Hawker. Any unpolluted pond or stream will be frequented by a busy population of males marking out their territories8. The mature male seems to have a complex eye colouring, showing eyes that are red at the top and brown yellow below, with a crimson frons. The thorax is yellow and brown with red colouring on the wing attachments, as in the male in the image above. The abdomen is crimson, showing tiny black spots on six of the abdomen segments, some of which can also be seen in the image. All dragonflies have ten abdominal segments. In the sunlight, the outline of the wings of this species looked golden through my binoculars, sadly this was not reflected in the images I took with my camera.
Sally Westwood
Sally Westwood is a Psychologist, and works as a researcher. She has taught in higher education as an English Language teacher. Her interests are varied. She has written many articles for Bird Magazines and Journals. She is also a professional bird photographer. Birds are her passion. She loves to draw and paint birds. She lives on a boat on the Deben and loves to sit and be with the birds, simply watching and photographing birds, in their daily activities.
Footnotes.
1. McGeeney, A. (1989)A complete guide to British dragonflies. Jonathan Cape.
2 As above.
3 Oelmann, Y. et al., (2023) Autumn migration of the migrants hawker (Aeshna mixta) at the Baltic coast. Movement Ecology, 11: 52. doi: 10.1186/s40462-023-00415-
4 McGeeney, A. (1989) As Above.
5 Knoblauch A., Lázaro, A. and Nilsson, C. (2021) ‘Autumn southward migration of dragonflies along the Baltic coast of Latvia’, Animal Behaviour, 179, pp. 81–90. doi: 10.1016 j.anbehav.2021.06.013
6 Oelmann, Y, et al., (2023) As above.
7 Knoblauch et al., (2021) As above.
8 McGeeney, A. (1989) As above.