Saturday, 30 May 2015

Northumberland's dragonfly battles: the contenders are hotting up

The male Broad Bodied Chasers have got all dressed up for the summer.  It takes a week or so from when they first emerge as glittering, golden bundles of energy to acquire this fine blue. Slowly the males' abdomens darken then a haze of sky blue, called prunesence, coats their tails. The younger males look much like females except they have slightly narrower abdomens. They keep out of the way of the mature males in their blue war paint, hanging around hedgerows and paths rather than risk conflict with their older kin. This nervousness changes once their blue fighting and mating colours have developed . Then it is time to head to a pond and challenge for a territory. These Chasers fly fast, often low but with erratic zig-zags, back and forth across ponds, even small, garden sites. They do not mind nearly dug out pools and are happy in cities. Every few minutes the territorial males perch on obvious branches and stems, and you can get close (the photo above was taken with an ordinary digital camera, not a telephoto). They are much more concerned about air-borne rivals than sneaky humans.

Adult Broad Bodied Chasers are good colonists and can turn up almost anywhere. They may not have bred from the ponds across which they now patrol and fight. The best evidence for breeding is finding their larvae, called nymphs, or the cast skins left behind as adult emerge. These skins are called exuviae. They are as gnarly and peculiar to look at as the adults are glamorous and racey. Here is one, the exuviae looking like some parchment mould from which the adult has been cast. The wispy white strands are where the cast skin ran inside the length of the breathing tubes, (trachea), that ramified into the body of the larva to carry oxygen. When the adult emerges and pulls itself free of the old skin these are pulled inside out a bit like when you take off a jumper or coats and the sleeve gets pulled inside out. The dragonfly season is hitting its stride. Northumberland remains a poorly recorded county for dragon and damselfies, even areas such as Druridge Bay that attract good numbers of bird watchers and outdoor enthusiasts. Northumberland is a region into which new species have expended from further south, and the east coast of England is the likely first land fall for occasional vagrants from the continent, just as with rare birds.  The western hills and bogs are even less recorded. Well worth watching out, you are very likely to find something new.

Tuesday, 26 May 2015

The damselflies get ready to party

Like their larger cousins the dragonflies the damselflies are also hatching earlier, by several weeks. Here is a newly emerged damsel that has fluttered to a perch on which to hide. If damselflies had to catch their breath, this is the moment. When they first heave themselves out of the old larval skin, left clinging to a stem of reed or grass around the edge of the pond, the newbie adults are dull coloured and poor flyers. The blues, reds or greens of the mature adult have yet to burgeon and instead the dull, faintly marked brown intermediate is called a teneral. This one had just about made it to a handy branch, then snuck around the other side where it thought I might not see it. At this stage it can be hard to identify the species but this one if likely to be an Azure Damselfy, which are one of the most common. A give away is the dark line that runs diagonally to about half way across the thorax, in the photo just to the bottom right of the thick black bar that runs the length from the wing bases to the rear of the neck. This half-a-line is typical of the Genus  Coenagrion and in Northumberland Coenagrion puella, tha Azure damselfly, is the only likely find. That is a bit of a cheat, I know. It could instead be a remarkable find of a species never before found up here, and I will double check. For now I did not want to scare the little damsel. It feels a bit intrusive, sneaking up to gawp as it gets changed to dance and fight away the days of summer in search of a mate.

Wednesday, 20 May 2015

A glamoruous dragonfly hints at summer’s warm days.

This exquisite creature is a Broad Bodied Chaser dragonfly, newly hatched and showing itself off  in the mid May sunshine. These are musclely, showy critters spangled gold when they first emerge. When they take to the wing it looks like someone has chucked a fistful of cheap and cheerful chocolates in the air, wrappers glittering. They are also confiding, allowing a close approach, confident in their getaway speed. Like many dragonflies they wiggle and tilt their heads as you sneak up trying to catch a better view of you. This one was loitering in Newcastle today. I am not sure if they have established at Druridge  Bay, but they have been moving north over the last twenty years, like so many of their relatives. Broad Bodied Chasers are often very quick to turn up in new ponds, even sites with very little vegetation. This individual may be a male or female. The females stay this beautiful collage of gold and browns whilst the males develop a powder blue coating over the abdomen as they mature. Newly hatched males have the same colours as females maybe to reduce trouble from their older kin who see off contenders for the same territories in aerial duels.
I found this one today three weeks earlier than I normally spot them, and the first Common Blue damselflies were fluttering up too, also early. Keep your eyes open along the Bay. The coastal wetlands are top spots for dragonflies and damselflies in the north east but under-recorded. I suspect there are many dragonflies  to be found between Cresswell and Amble that we’ve not noticed before and these unusually early arrivals may be a good omen