Tuesday 24 July 2018

National Dragonfly Week 2018

As alluded to in the previous post, Saturday 21st July saw the beginning of 2018's National Dragonfly Week, as decreed by the British Dragonfly Society. Locally, I ran an event under the auspices of the Orkney Field Club, promoted through the Club's web page and Facebook site, as well as on the Odonata-centric OrkOdo page.

Nine hardy souls braved the early morning wind and rain to meet at the ferry terminal at Lyness in Hoy, for a gentle amble up to some bog pools on the southern side of Wee Fea. The eight folk who joined me varied in dragonfly experience, but they each brought plenty of enthusiasm for all wildlife, so prospects were reasonable for a good day.

The initial climb was quite sheltered, but two miles later, as we neared the first pools, a westerly wind was beginning to make its presence felt. In the absence of any direct sunshine, there weren't any dragons or damsels on the wing, so we began to search for roosting individuals amongst the rushes at the pool edges.

The group soon spotted a few Emerald, Large Red and Common Blue Damselflies, and began photographing the more approachable insects, a task made trickier by the afore-mentioned breeze.

Photo courtesy of MT
As I was explaining a few details of the life cycle of dragonflies, JT made the discovery of the day (ok, I called it early, but I was correct) by finding a recently-emerged Common Hawker dragonfly. Reasoning that it had not yet moved far from its emergence site, I was able to spot its exuvia, the shed larval skin, the only remnant left of the insect's several years spent as an aquatic creature. Although we didn't see any more Common Hawkers on the day, we did find six exuviae, proving that the species was breeding at these pools.

Photo courtesy of JT

As the clouds thinned and the temperature rose, a few Black Darters flew by, most of which were yellow and looked as though they had only recently emerged. However, the occasional mature individual was seen, including this male which actually became too hot in the brief spell of warm sunshine. It began 'obelisking', pointing its abdomen towards the sun, effectively limiting the surface area of its body able to absorb heat from the sun.

After a picnic lunch, we began the return descent back down the hill. The second site for the day was a larger bog pool which was located in a more sheltered location in the lea of the hill. For this reason, there were many more insects present, with butterflies, moths, bees and hoverflies all vying for our attention. But perhaps the most intriguing find was a Marsh Speedwell, a small plant with the characteristic blue Speedwell flower, but with leaves more akin to a Willowherb.

This site was predominantly populated by Black Darter and Emerald Damselflies.

The female damselfly above was in tandem with a male, but she didn't seem the slightest bit interested in mating with him, resolutely refusing to take their relationship to the next stage. However, she was having to be very patient, because until the male became bored and released her, she was rather stuck.

Here's a happier shot, of a pair of Emerald Damselflies ovipositing. Well, actually, it's obviously the female who's egg laying, but her partner is guarding her from other suitors.

Photo courtesy of PM
Another floral note at this site was a rather picturesque aquatic plant, Least Bur-reed Sparganium natans, many thanks to JC for the ID.

Our last target water body for the day was a pool beside the Scapa Flow Visitor Centre. This pool is less acidic, much more duck-infested, but blessed with pond weed and plenty of emergent vegetation. As well as more Emerald and Large Red Damselflies, we found several Blue-tailed Damselflies to take our species tally for the day to six.


Sian said...

Many "firsts" for me on that trip. Thoroughly enjoyed the day. So many "jewels" to see at every turn once I got my eye in! Thanks for organising the day so well.

Imperfect and Tense said...

You're very welcome, Sian. I'm glad that all the planets aligned (well, ferry timetables) so that you could make it. Especially as you brought banana cake!

Anonymous said...

I never knew about obelisking, fascinating stuff. You got a reasonable haul, given the weather. I saw a black-tailed skimmer last week in a hay meadow and thought of you. Lovely insect it was, sat for ages on a stem of grass. Golden-ringed are around here too. A few hawker exuvia on the vegetation around our pond but less than normal I think. Would the hot weather have affected them?

Imperfect and Tense said...

That is a very interesting question, CT. I've been pondering what the effects of this hot spell might be, both for now and subsequent years. There's been little comment on dragonfly webpages about it. Certainly, water bodies are drying up, even here, which must give the larvae an emerge or die choice. It is possible for larvae to delay emergence in bad weather, so I wonder if they have a similar tactic for emerging early in good weather (although they'd likely not be fully grown)? And then, of course, what about the coming years? Fewer dragons now, fewer water bodies for eggs and larvae, how will that affect future populations? Any trend will be noticeable in damselflies first, as they usually have a larval stage lasting a year. For dragonflies, it will take a bit longer to know, maybe two to three years. You have prompted me to ask the question!

Lucy Corrander Now in Halifax! said...

I love to see damselflies but find dragonflies somewhat disconcerting.

I didn't know about obelisking before. If I see an insect in this position I will reconsider it in the light of the light of the day.

Imperfect and Tense said...

Lucy, it isn't often that it is hot enough in Orkney to witness this behaviour!