Tag Archives: Migrant hawker

Back yard safari

Posted on September 15, 2012 | 20 comments

A couple of posts ago I described my Fenland safari and since then I just happened to have had my own ‘back garden safari’! Lots of colourful creatures have been stopping by to refuel.

I’ve previously expressed concern for the depleted populations of insects, in particular butterflies and dragonflies, due to the mad weather we’ve experienced in the UK this year, but in the last couple of weeks there have been some great sightings outside my back door.

Common darter (Sympetrium striolatum) female perched on the clothes line

The dragons have been late to appear but since the last week in August there have been common darters regularly alighting and migrant hawkers hunting overhead.

And of course it’s that time of year when the arachnids are most in evidence, and my garden is festooned with garden spiders, there are webs attached to every surface: walls, plants, windows… everywhere.

Garden spider female, Araneus diadematus, despatching her prey, a small fly

The female garden spider has a bulbous abdomen which is adorned with the fabulous diadem that gives the species its name. The male is smaller than the female and has a flatter, kite shaped, abdomen, but he also carries the diagnostic markings. A couple of years ago I posted about the perilous love life of the garden spider, suffice to say the sex life of the male can be dramatically and terminally curtailed if he fails to show the lady sufficient respect!

This garden spider male set up home inside the bedroom window – until the resident arachnophobre found him and relocated him

As well as the spiders, the occasional cricket strolls by, and this little chap was taking shelter under a sunshade from the unseasonally hot weather last weekend:

Oak bush cricket – Meconema thalassinum – the male of the species. The female has a long, upturned ovipositor protruding from her rear

The oak bush cricket is quite a small example of the genre, they are 13-17mm long and are carnivorous, feeding on small insects. They live on the edge of woods and in gardens and appear from July into the Autumn.

Also putting in a welcome appearance was a common buzzard, Buteo buteo:

The buzzard has been one of the birds which has really bounced back since the more stringent controls on of agricultural pesticide use were introduced in the 1980’s. I’d never seen a buzzard until I was in my 20’s and even then it was the occasional sighting in the wilds of west Wales or down in Cornwall. But they can now be seen over all of England – even from my garden.

Hoverfly – Volucella inanis

Hoverfies rarely have common names, they’re simply known under the generic name ‘hoverfly’. And V. inanis is no exception, at least as far as my research reveals. There was great excitement when it first buzzed into the garden because at first glance we thought it was a hornet due to it’s size and its yellow and red colouration. And it was a whopper! They can grow up to 15mm long and this one was one of the bigger ones. It eventually settled and posed rather obligingly on the edge of the rabbit run while I snapped a portrait, and it is a very handsome fly. It has an interesting breeding tactic too laying its eggs in the nests of other social wasps, including hornets – which probably explains its size and colour scheme – where they hatch and feed on the larvae of the host.

Comma – Polygonia c-album

I waited expectantly for this comma to open its wings and show the gorgeously ragged orange symmetry, but it didn’t. So I had to content myself with this silhouette of it perched on a cooking apple.

20 Comments

Posted in Anisoptera, Arachnids, Birds, Birds of prey, Butterflies, Crickets, Darter dragonflies, Diptera - two winged flies, Dragonflies, Hoverflies, Insects, Ornithology, UK wildlife

Tagged arachnids, Araneus didematus, Buteo buteo, comma, common buzzard, Common darter, darter, Diptera, dragonflies, garden spider, hawker, hoverflies, insects, Meconema thalassinum, Migrant hawker, oak bush cricket, Othropera, Polygonia c.-album, Sympetrium striolatum, Tettagonidae, two winged flies, Volucella inanis

Damsels of Fen Drayton

Posted on June 24, 2012 | 29 comments

One of the reasons for my trip to Fen Drayton a few weeks ago was to have a look to see which of our dragonflies were out and about. I went in early June and that time of year is a little early for the true dragons to have emerged, although it’s not impossible. But despite the shortage of the true dragons, the hedgerows and lake sides were abuzz with damselflies.

Male red-eyed damselfly – Erythromma najas

Dragonflies and damselfies are the two members of the taxonomic order ‘Odanata‘ or Odanates. There are two sub-orders within the Odanata: the Anisoptera – the true dragonflies, and Zygoptera – damselflies.

Azure damselfly – Coenagrion puella – the blue form of the immature female

Damselflies in the UK are approximately 4-5cm (1.5-2 inches) long and have thin abdomens and are all smaller and more delicate than the chunkier dragonflies. Having said that, the biggest living Odanate is currently a damselfly who resides in the rainforests of Central America, it has a wingspan of 19cm (7.5 inches) and the abdomen is 10cm (4 inches) long. A real whopper!

Blue tailed damselfly – Ischnura elegans – immature femaleBlue tailed damselfly – immature male – Ischnura elegans

Male and female Odanates, and immature and mature individuals, can often be distinguished by colour. The common blue female below is conspicuously brown so the species gets its name from the electric blue colour of the male. The common blue can easily be confused with the variable damselfly which is the same blue colour, but they are distinguished by the black markings on segment 2 of the abdomen which is shaped like a goblet on the variable and a club on the common blue. Also, the antehumoral stripes (on the side of the thorax) are complete on the common blue and broken on the variable. Although, as the name suggests, the variable is indeed variable and it can make distinguishing the two species a little tricky.

Common blue damselfly female – Enallagma cyathigerum – the only common blue we saw on this trip, perched on my friends finger

The black goblet on segment 2 is visible under the front of the wings on the variable damselfly below. But confusingly, it’s living up to its name because the antehumoral stripes are unbroken.

Male damselflies have two sets of paired claspers at the end of the abdomen which it uses to clasp the female on her pronotum, which is the protrusion in the middle of the back of the head. The claspers have tiny hooks on them which match grooves in the female pronotum and in order to avoid procreational mismatches the hooks and grooves are species specific.

Variable damselfly – Coenagrion pulchellum

In the picture above a variable male has clasped his lady by the pronotum. Male damselflies have primary genitalia at the end of the abdomen on the 8th segment, but in order for fertilisation to take place he needs to transfer a ‘spermatophore’ from the primary genitalia to the secondary genitalia on the second segment at the thoracic end of the abdomen. The female then curls round in to the ‘wheel’ position to transfer the sperm to her genitalia which are underneath her 8th abdominal segment.

A pair of variable damsels in the wheel position

All the Odanates are carnivores, and the larvae which hatch from eggs layed under water are ferocious carnivores, the larger ones will even take small fish! On one occasion last year while I was photographing large red damselflies (Pyrrhosoma nymphula), a large hawker dragonfly (I think it was a migrant hawker, Aeshna mixta) which had been buzzing around higher up for several minutes suddenly dived down and caught one of my large red damsels. In a few seconds the migrant butchered it and ate it on the wing and the inedible bits of wing and leg were discarded and rained down around me.

Scarce chaser – an immature male

A lone Anisopteran, or ‘true’ dragon was spotted on this trip and it was an immature scarce chaser, Libellula fulva. He was a lovely mustard colour and he can be differentiated from the female by the colour of the thorax which is dark grey in the female, and from the male adult who is electric blue. He undergoes quite a transformation in transitioning from immature to adult.

29 Comments

Posted in Anisoptera, Chaser dragonflies, Countryside walks, Damselflies, Dragonflies, Fen Drayton, Fen Drayton nature reserve, Hawker dragonflies, Insects, RSPB reserves, UK wildlife, Zygoptera

Tagged Aeshna mixta, Anisoptera, azure damselfly, blue tailed damselfly, Coenagrion puella, common blue damselfly, damselflies, damselfly mating, dragonflies, Enallagma cyathigerum, Erythromma najas, Fen Drayton, insects, Ischnura elegans, large red damselfly, Libellula fulva, Migrant hawker, Nature, Odanata, Odanates, Pyrrhosoma nymphula, red-eyed damselfly, RSPB, scarce chaser, true dragons, wheel position, wildlife, Zygoptera

Autumnal Anisopterans

Posted on October 28, 2011 | 1 comment

Yesterday, 28th October, was one of those glorious sunny autumnal days where the air was fresh but the temperature was raised by bright sunshine, and I’d heard that the winter migrants were arriving on the lakes at Milton Country Park on the northern edge of Cambridge. So I took my camera to work and headed there for a stroll at lunchtime in the hope of snapping a teal or wigeon or perhaps a more unusual visitor. Several waterbirds were on parade including these cormorants:

Several migrant duck species were there too, including wigeon (Anas penelope, Dansk: pibeand), the duck with the chestnut head in the background of the cormorant picture is a male wigeon, tufted duck (Aythya fuligula, Dansk: troldand):

A male tufted duck resplendent in his pied plumage and bright yellow eye

…and gadwall (Anas strepera, Dansk: knarand).

What I didn’t expect to see though, certainly not in the kind of numbers present, were dragonflies. It’s nearly November and the weather has started to get more autumnal but the warm weather up to now must have suited these airborne predators. In particular common darters (Sympetrium striolatum) were conspicuous, six at one time including two mating pairs. It’s always a treat to watch dragonflies but especially on a sunny day at the end of October, living uo to their name and darting about making a loud low frequency buzzzing noise .

Stunning symmetry of a pair of mating common darters

The darters were sunning themselves on the fence lining a viewing jetty on the edge of a lake and while they were busy warming and copulating a migrant hawker (Aeshna mixta) was patrolling the adjacent reedbeds. All the dragons were pretty much oblivious to my presence unless I ventured too close then they would rise into the air, the copulating couple in tandem, only to return to pretty much the same spot with 30 seconds or so.

Migrant hawker

Every so often one or more of the common darters would chase the hawker away until it lived to its name and plucked one of them out of the air and butchered it whilst flying around our heads, scattering the inedible parts around us. After its aerial snack it headed up into the treetops and disappeared.

The hawker missed a trick. It went to alot of effort catching its darter on the wing when it could have had twice as much protein if it had spotted this pair. But I’m glad it didn’t!

1 Comment

Posted in Anisoptera, Birds, Darter dragonflies, Dragonflies, Insects, Milton Country Park, water birds

Tagged Aeshna mixta, Anas penelope, Anas strepera, Anisoptera, Autumn, Aythya fuligula, Cambridge, Common darter, cormorant, dragonflies, gadwall, knarand, Migrant hawker, milton country park, Phalacrocorax carbo, pibeand, skarv, Sympetrum striolatum, troldand, tufted duck, wigeon

Dragonfly discoveries

Posted on October 19, 2010 | 1 comment

Dragonflies are amazing insects which it seems can be seen just about anywhere. In 2010 I’ve even spotted them over my garden in Histon. It occurred to me I should put some effort into photographing and learning about them as I sat with my family eating a picnic on a bench overlooking the fountain in the Cambridge University Botanical Gardens. Numerous small, magnificently bright red, individuals were whizzing around the pond, and a few big blue ones a short distance away from the pond (the small red ones were a species of darter, and the big blue ones were hawkers – probably migrant hawkers). I attempted to photograph these for subsequent identification but alas my photographic skills were’t up to the job on that occasion. Despite that I looked up some information and lots of great pictures at http://www.dragonflysoc.org.uk/home.html. This is a great website and started me off on a journey of discovery which is now pretty much finished this year but which I plan to resume as soon as possible next year.

Subsequent walks around Milton Country Park and the fields north of Histon provided lots of opportunities to see many species of dragonflies and damselflies:

Female brown hawker sunbathing on a birdbox at Milton Country Park

Migrant hawker male. The yellow ‘golf tee’ on segment S2 is diagnostic

Dragonflies originate from species which fossil records date to the Carboniferous period, around 300 million years ago, and could have a wingspan up to 70cm! They comprise the taxonomic sub-order known as ‘Anisoptera‘ and are part of the order ‘Odonata‘ which also includes damselflies (Zygoptera) and another group which is virtually extinct called ‘Anisozygoptera‘. There are now around 5300 species of dragonflies of which approximately 40 reside in the UK.

Dragonflies lay eggs underwater either loose, protected by a hygroscopic gel, or inside plants. The eggs of some species can lie dormant over winter and resume development when temperatures rise in springtime. Time to hatching is temperature dependent but is usually around 2-5 weeks and the larvae develop in water, all British species overwinter once as larvae but time to adulthood can be up to 5 years. Metamorphosis from larva to adult is triggered by increasing day length and temperature in spring, and includes the transition to breathing air and growth of their incredible compound eyes. Each eye is made up of around 29000 individual elements called ‘ommatidia‘. They also possess three addtional ‘simple eyes’ call ‘ocelli‘ which are sensitive to light intensity and assist in controlling flight via direct nerve connections to the flight muscles. Dragonflies have excellent colour vision and can also see ultra violet light. It makes me wonder what the neural activity behind all that optical prowess is capable of: are dragonflies merely responding directly to visual stimuli via reflex arcs, or is there more sophisticated image processing going on?

Common darter, immature male

Common darter, female. Note the compound eye.

Dragonfly larvae are ambush predators feeding on moving prey including other insect larvae, snails, small fish and tadpoles. Adults catch other insects in flight, holding their legs out in front like a bread basket to scoop prey from the air such as flies, flying ants, mosquitoes and even other, smaller, dragon flies.

Newly emergent dragonflies are powerful fliers and disperse widely. They are often seen a long way from water and can even cross seas. They reach maturity after a few days to a few weeks, a process also controlled by temperature, when the males will congregate at vantage points near water where females come to oviposit. The male will grasp the female around the head with his anal appendages and attempt to mate with the female by swinging her round to form the ‘copulatory wheel’ enabling him to pass a packet of sperm from the secondary male sexual organs located on his second abdominal segment to the female sex organs located on her eighth abdominal segment. After mating, sometimes under the guard of the male, to ensure his sperm is not displaced by another male, the female will oviposit underwater. And so the cycle begins again.

Broad bodied chaser – female