Wednesday, 21 July 2010

Changing Skins

Walmer Castle is a real gem and one of the best of English Heritages sites in Kent. But at this time of year it isn't the castle and it historical contents that bring me here, too many summer visitors for that. It is the formal pond in the garden that I go to visit.

Small Red-eyed Damselflies were first observed in Britain in July 1999, at Bradwell-on Sea in Essex, and I actually went there to see them. They reached Kent in 2001, when Barry Wright found some at Bluewater. Fortunately they have spread from there, as I have resolved NEVER to go the Bluewater.

Small Red-eyed Damselfly pair (Erythromma viridulum)

The species is now quite widespread in Kent and Walmer Castle is the nearest site I know to St Margaret's where they are breeding. When I arrived today it was quite overcast and there were just a few to be seen on the Water Lily leaves.

I found one that had very recently emerged. The nymph, that has spent the last year in the pond, crawls out onto a leaf, and when it's casing splits the Damselfly emerges. At first all the external parts are soft and colourless and it takes time for the adult to become "air-worthy" as the wings have to be pumped up and hardened.

The last "skin" of the nymph is left behind. This is known as the exuvia and experts, like John and Gill Brooks are able to identify the individual species from this piece of jettisoned evidence.

Their book say the the male has fine antehumeral stripes on the thorax, but I've never been able to see them. However on the picture above I do believe there is just a hint of a yellow stripe.

When the sun came out a male and female Emperor Dragonfly began to fly up and down the pond. I noticed the female landing in amongst the lilies, ovipositing (laying eggs).

A closer look showed that this female was still in quite good condition, normally I find the females laying eggs have very battered and tatty wings, presumably the result of some very vigorous "courting" by the eager males.

Emperor Dragonfly female (Anax imperator)


Phil Smith said...

Hi Tony
there are small red eyes at samphire hoe not sure if walmer castle is nearer or not.

Tony Morris said...

Hi Phil,
As the crow flies.8.26Km to Paul's office and 5.24Km to Walmer Castle from my house.