Friday, May 27, 2011

A damsel emerges from the deep...

May 16th started much like any other day of late. Already sunny and warm by 7am. It's been a fabulous start to the season for sunshine with a 50 day period of no rain at all locally.

I was already out and about with the dog by 7.30am enjoying another spring day.I've been keeping an eye on several small ponds for damselflies and dragonflies, and on this particular morning thought I'd see what was about at a man-made pond in the corner of a meadow that has been left uncut for sometime now.

Herbie, the terrier, knows the score when we arrive at this pond. We've visited it so often since winter that he knows he's in for a bit of a wait whilst I take some pictures. He takes up his usual position on a bank alongside a rabbit warren and there he stays, hoping!

I quickly scan the area for anything of interest and immediately my eye is drawn to a small 'blob' on a lilly leaf. Investigating further, I realise that the blob is in fact a damselfly nymph that must have emerged from the water in the past few minutes.

Not having seen this before, and not wanting to miss anything, I set the camera up best I can and can see that the nymph is slowly making it's way on to a nearby stone. I decide that I'll try and record the emergence with a series of photographs and position myself on the (damp) ground beside the stone.

The following set of photographs (there are a lot, but bear in mind I actually took 160 on the day) chronicles this amazing metamorphosis from the nymph that one moment is living underwater, to the air breathing insect that it is to become a short time later.

The nymph emerges from the pond
It was around 9am when the damselfly nymph first climbed out of the water and on to the nearby stone.

 The first thing I noticed was a small, cross-like shape appear on the abdomen of the nymph. This was just above the two tube-like shapes that contain what will become the wings.This began to expand and swell as the nymph seemed to be pumping itself up in order to break through.

9.07am: The very pale abdomen of the emerging damselfly becomes visible for the first time. The insect is still pumping hard all the time. At this stage, the emerging insect is a really pale colour. 

9.09am: More of the abdomen emerges and the insects eyes begin to separate from the nymph's as well.

The effort required for this transformation seems to be huge, the damselfly spasmodically pausing before resuming the pumping action that is gradually freeing it from its old life.

9.10am: The whole of the insects head, eyes and thorax are free and although as mentioned, the markings are pale, they are distinct even now.

At this stage, another short rest was required before the struggle for freedom was rejoined.

9.12am: The insects legs begin to appear but once again, the effort seems to have been too much for the little thing and once the front legs had emerged the pumping actions ceased. 

9.16am: After what seemed like a long wait, but was actually only 4 minutes, there was a little movement of the legs.

9.21am: After another break the pumping actions begin again and the abdomen starts to emerge. The legs are put to the ground for the first time too. It's now 20 minutes since the nymph emerged from the pond and still the insect isn't fully emerged and remains in a very vulnerable state.

9.24am: The damselfly now arches it's back and this action encourages the emergence of the rest of the abdomen.

A few moments later and it's now almost totally free apart from the back legs.
Now recognisable as a damselfly. It is however very soft-bodied and there's little sign of the blue colour it will become.

9.26am: Almost half an hour of struggling and the damselfly is now free and has moved to one side of what can now be referred to as the exuvia some blueish colour is now visible but it remains very pale.

9.30am: Yet more pumping has resulted in the abdomen starting to lengthen until it is equal to, and then exceeds the exuvia. Whilst the abdomen was increasing in size, each pumping action moved the damsel backwards a little until it was positioned behind the exuvia.The wings remain just stubby little, crumpled things at this point.

9.35am: The insect begins to move around on the stone, arching it's back in strange, dance-like movements and now the wings begin to lengthen too.

Now the insect is gaining control of its limbs and seems to be able to move more freely. The wings are now much longer, although still crumpled.The blue colour on top of the abdomen begins to darken.
It become obvious to me that the damselfly's instincts are now at work and its movements are becoming more determined and directional. It's looking for something?

An overhead view

9.40am: What it was looking for was a stem to climb to continue the process of drying out and hardening up. It found the nearest one available and climbed to the top. There it sat, swaying in the cool breeze. Its wings now as long as the abdomen and growing all the time. They were also becoming transparent as they began to harden.


I'd now been watching transfixed for close to an hour. I couldn't believe how lucky and privileged I'd been to witness this first-hand.
I still have difficulty in comprehending just how this whole process works. At what stage, I kept asking myself, does the water-bound insect 'die' and the damselfly is then 'born'?

It's a miracle of nature that happens thousands of times each spring, but how many of us are lucky enough to have been there at just the right moment and seen it all?

Herbie the terrier had been quietly sitting on the other side of the pond to this action, watching for his rabbits for all of this time. He was quite happy and would have been contented to stay for another hour no doubt. Time was moving on though and much as I would have loved to stay and seen the whole thing through to its first flight, I decided perhaps I should make a move, before the search party arrived for me!

Who would have thought that the strange looking brown 'blob' that emerged from the pond an hour ago. and was now awaiting natures final touches, would a couple of hours later look like this?

And so a truly memorable experience came to an end. I apologise for the length of this blog entry but I've trimmed it down as far as I dare without losing vital content. I hope you have found it interesting.

Until the next time....

Monday, May 16, 2011

When is a caterpillar not a caterpillar?

Today I want to concentrate on the humble caterpillar.
We have all seen at least the more commonplace ones from time to time, but do we actually know what we're looking at?

For instance, is this a caterpillar?

What about this example then?

Or how about this weird looking creature?

Here's a face-on view of this one if it helps?

One more chance to get it you think this is a caterpillar?

Unsure? Do you perhaps think that these are all caterpillars? Maybe, none are?
The truth is that you would need to have chosen the third & fourth pictures (The weird creature!) as being the only true caterpillar amongst those examples.

If you did, then congratulations, you probably know your caterpillars and won't need to bother reading the next section of this blog.
If that has surprised you, or confused you, then I'll try and explain.
Let's start by taking a look at a diagram of the parts of a caterpillar...

Caterpillars come in many colours, shapes and sizes. Some are hairy, some not. Regardless of these differences they all share certain morphological features.

The diagram above shows these features.
1. Head
2. Thorax
3. Abdomen
4. Segment 
5. Horn
6. Prolegs
7. Spiracle
8. True legs
9. Mandible
10. Anal prolegs

The important part of this information, as far as a quick identity check goes is the amount of legs.
If you are unsure as to whether you are looking at a caterpillar or not, count the prolegs. Caterpillars may have up to five pairs of abdominal prolegs, but never have more than five.

Caterpillars are the larvae of butterflies or moths and belong to the order 'Lepidoptera'.

If the caterpillar/larva you are looking at has more than five pairs of prolegs, then it's likely to be a sawfly larva.
Sawfly larvae look very similar to caterpillars but are an entirely different kind of insect.
Sawflies are related to bees and wasps and belong to the order 'Hymenoptera' Like caterpillars the sawfly larvae also feed on plant foliage.

Close-up of caterpillar prolegs

And so, it's a fair bet that if the insect has 6 pairs of legs or more, it's probably going to be a sawfly but definitely isn't going to be a caterpillar.

A sawfly larva (count the legs)

Caterpillars don't breathe as we do of course. They use the spiracle to 'exchange gases'. They do require oxygen to live, just as we do and produce carbon dioxide as a waste, just as we do.They don't however have lungs to transport oxygen around the body. Instead they use a series of tubes called the tracheal system to perform the gas exchanges.

This system can't be controlled by the insect and only proves efficient for small  organisms. If this were not so, we might find ourselves living with giant insects (now there's a thought).

So there you have it. The rough guide to caterpillars.

Until the next time then...

Friday, May 06, 2011

Damsels and Dragons...

Looking back over my last blog entry, I see now that it was a bit 'wordy' and so, as this is primarily a photo blog, I've decided to let the pictures do most of the talking this time.

First up is a photo of a newly emerged Damselfly. These are very pale when they first emerge but colour-up quickly. They are also unable to fly until they have pumped their wings up to full capacity, and so they are good subjects for a few shots.

Once able to fly, the next thing on the mind of a damselfly that would be no more than an hour old at most, is food. They are voracious eaters and will munch through a good number of bugs and insects.

Once suitably fuelled, they would be looking to breed. 

These are actually dragonflies pictured here but damselflies also adopt the same 'wheel' position for erm, erm...well...reproduction purposes.

Damselflies come in a fair variety of colours and sizes, although all are smaller than the dragonflies. Picture below is a  'White-legged' Damsel.

Amongst the most beautiful of our native damselflies are the delicate 'Beautiful Demoiselle' (Calopteryx splendens). These are around between May & September and despite the 'old wives tale' do not live for only a day.

All of the damsels are weak-flying and have four wings that are generally held vertically above the body when at rest.
Although they do colour-up fairly soon after emerging from the larval case, they don't acquire full colour for several days.

As you'll be able to see in the above photograph, dragonflies are somewhat sturdier and of a heavier appearance. This one is a Broad-Bodied-Chaser (Libellula depressa) and these have a particularly broad abdomen, hence the name.

The strange looking thing below the dragonfly image is the larval case, or skeleton as some refer to it, of the dragonfly. Seen from below it shows the strange appendage under the 'chin' that's always fascinated me. I really should do some research and find out just what it's purpose is/was.

A blog entry wouldn't be complete without a spider shot and I'm sure there will be those amongst my readers who would only be disappointed if I failed to include one and so today, it's the turn of another crab spider.

The other thing of note that's been happening locally is the ever increasing amount and diversity of bug nymphs (youngsters) that are emerging almost daily now.

 It's that time of year when every time I walk the Kent countryside around my home, I just never know what I'll find. The exciting thing for me is that most of the bugs go through around four or five 'moults' and with each one, there emerges a slightly (or in some cases very) different looking creature.

By the way, how many realise that spiders moult too? Yes, the whole front of the abdomen splits open and the spider crawls out leaving behind the 'exoskeleton' complete with eye membrane.

Spider moult

Leptopterna sp Bug nymph (I think)

Cyllecoris histrionius (A Mirid Bug nymph)

That's about all for this entry. I hope to be back fairly soon with another entry.

By the way, in case you weren't aware of it, you can view a larger size of any of the photographs in each blog entry by just clicking on the chosen image.

Until the next time then...