Bio-security conundrums

Whilst there's plenty to worry about in Orkney at the moment, what with avian flu killing seabirds and wildfowl, and remembering that the threat of non-native invasive mammalian predators has not gone away, I have had a few bio-security issues of my own recently. Admittedly, minor issues in the grand scheme of things, but if the consequences, however unintended, are unknown, then who knows what is major or minor?

A month ago, when we were on holiday in the Cairngorm area, we had a salad accompaniment to one of our evening meals. So far, so healthy, right up to the point where I found a dead larva of a ladybird amongst the greenery. Well, I say 'found', I mean nearly ate. The previous day had been World Environment Day, so perhaps that was on my mind as I casually moved the tiny corpse to the side of my plate and finished the meal. As Megan commented at the time, it was a positive sign that the salad crop had been a home to natural predators rather than innumerable sprayings of insecticide. The packet from the supermarket did say 'Wild Rocket', so fair enough!

Hah, 'on the side of my plate' was likely to have been the warmest the wee beastie had been in days, as it had been in our fridge for 48 hours, and who knows how long on a supermarket shelf before that... and previously in a refrigerated delivery lorry... and likely at a packing or distribution point before that? So, you know how this goes, right?

Dead beastie + Warmth = Not so dead, but only chilled, beastie

I watched, fascinated, as the larva wriggled a bit, as if waking up from a deep slumber, and I thought "Wow!", followed quickly by "I wonder what species of beetle it is?" Ah, but then came the realisation that I didn't know where it was actually from? Retrieving the empty plastic salad bag from the bin, I was relieved to note 'Packed in the UK', but then moments later saw the legend 'Origin: Italy'. Dang, was this a UK species or not? How ever much I wanted to cheer for the little bug, I knew I couldn't release it into a Caledonian pine forest, just in case.

Fortunately for me and my conscience, after half an hour or so, all signs of bug life had ceased, removing my conundrum if not my indigestion.

A few days later, whilst watching dragonflies and damselflies at a couple of ponds at the edge of a wood in the village of Nethy Bridge, I spotted an exuvia, the shed larval skin, of a large hawker dragonfly. The larval skin was clinging to a dead plant stem at the water's edge, its owner long gone as it became an aerial predator after several years as an aquatic one. Although we didn't see one of these adult insects all holiday, the location and habitat indicated that this would likely be a Common Hawker, but I retrieved the exuvia to confirm the ID later.

Photo courtesy of Megan Taylor

The exuvia then sat in the lounge of our accommodation for a day or so, until it was time to pack for the journey home. An empty houmous tub came in handy for its transportation back to Orkney and an appointment with an ID book.

It was another few days before I had time to sit down with said book and go through the key features of the exuvia...

Underside of exuvia

At 45mm in length, the exuvia was slap bang in the middle of the size range for a Common Hawker larva, 40-51mm. The labial mask (the hinged lower jaw) is approximately 2.25 to 2.5 longer than it is wide. On the abdomen, lateral spines are only present on segments 7-9, with the spines on segment 9 not reaching halfway down segment 10. All good indicators that this is indeed from a Common Hawker.

But... but the exuvia wasn't the only creature in the tub.

Don't worry, it wasn't a zombie ladybird intent upon murderous revenge, but I had no idea what it was, or even how it had got there. Was it inside the shed skin all along? Or had it crawled into the exuvia whilst it was sat in the lounge of the cottage?

In short, I needed an insect expert with the knowledge and patience to key out the tiny features which would identify the beetle to species. Ladies and gentlemen, I give you Alastair, author of the blog Literate herring, this way.

Alastair took on the challenge, despite having many ID conundrums of his own to solve, and within a day had come back with a positive identity for the tiny stowaway. It was Microcara testacea, and as its description on UK Beetles revealed, it was very likely to have been in the dragonfly exuvia when I recovered it, as these beetles live in permanently damp habitats in open woodland. Thank you, Alastair!

Now, a month later, as I write this post, I have revisited the plastic tub, and found another beetle, likely the same species, and very dead. Ecological conundrum crisis averted!