Hole in the Skye

It's time for a brief interlude in my 'Missing Month' series of catch-up posts....

Today, four of us braved the wet weather and met up for a Skye Nature Group visit to Orbost, which is situated pretty much midway between Dunvegan and Struan on Skye's west coast. I'd never been there before but Big John told me that it was "a lovely part of the world". Big John never tells lies, though he pushed it awfully close this time...

We arrived in the rain, held our walk in the rain, saw some stuff in the rain and then finally we departed. In the rain. Not entirely Big John's fault, I agree, but I blamed him nonetheless. Whilst standing in the rain.

Anyhoo...as per Stephen Bungard's instructions, we duly checked out a row of planted trees/shrubs/tall things, all or some of which may prove to be large Cotoneasters, or Stranvaesia, or maybe something completely different. I kept stuffing bits of branches and clusters of berries into my rucksack, I could probably have been arrested for deforestation had anybody thought to check. We also checked out a couple of Laburnums which keyed to either Hybrid or Scottish Laburnum, depending on how strictly you wish to follow the keys. I'd like to go back in dry conditions and try again. 

But the BIG news is that I found another moth new to Skye! Alright, so there's the small fact that it's been recorded here before. But other than that, it was new. Heck, I thought it was new at the time - and that's what's important, right? 

See that oval hole? And the brown line leading up to it? Good. Now read on....

So what we have here are a set of clues. I love clues! Anybody can whack out a light trap and see what species end up inside come morning time. But you need a few extra skills to find shizzle like this! I love it, I really honestly do. Take Luffia ferchaultella. Own up, who's ever had that at a trap, eh? My point exactly!

So here's the story. A newly-mated female Heliozela hammoniella moth only has one thing on her mind. Kids! So she diligently seeks out a suitable bit of birch, it has to be just right, up near the fresh tip is good. She lays an egg on the stem which then hatches out. The tiny newborn caterpillar squints in the bright light of day, figures it needs to get out of sight and grab a quick meal. It immediately burrows into the safe, dark, tasty stem. Thereafter it chews its way ever upwards towards the more nutritious leaf. Eventually it hits daylight as it breaks out of the stem and into the leaf blade. At this point our caterpillar is still small enough to fit between the upper and lower surfaces of the leaf. Just think about that for a moment. Have you ever tried to look at a leaf edgeways on? It's thin, very bloody thin, probably as thin as a £5 note, maybe thinner? And yet there's our tiny caterpillar, happily living inside that! 

Eventually, of course, our caterpillar grows too large to be constrained within green leaf tissue as thick as a £5 note, it needs to move on elsewhere. So what happens next? Wait up, I'm telling you. It chews its way out of the leaf tissue, walks across the leaf surface for the very first time in its life and then, using just its jaws, chews out a perfectly neat oval section of leaf. Then things get seriously weird! You remember back to when you were a kid and you used to wrap yourself up in the duvet covers and parachute to the ground? No? Oh ok, so maybe that was just me then... Anyway, our tiny caterpillar now grabs hold of a precisely excised plate of leaf which it then folds over and tucks in around itself until it has created itself a nice leafy sleeping bag. When it's happy that the fit is snug, it spins a line of silk from its mouth and lowers itself to the ground, far far below. Maybe as much as six feet below, and that's a whole lot of silk for a caterpillar that measures maybe 4mm from head to rearmost pro-leg. 

A picture is worth a thousand words, right? 

So, knowing the back story, check out the image above. We can see where the caterpillar has erupted upwards out of the stem and into the leaf blade. We can see where it chewed it's way through the leaf tissue from leaf base, heading upwards and crossing the midrib before growing much larger and fatter in the final stages of the leafmine - time to jump ship, guys! We can see where it left its constricting mine, walked diagonally across the leaf surface and excised a section of leaf to use as a cocoon during it's descent to ground level. Ok, so all that actually remains for us to see is our caterpillar's history, but bloody hell - how amazing a story does this one leaf tell us??? 

Personally I absolutely love stuff like this. Yeah, so a light trap will chuck bucketloads of moths your way. Light traps are a fantastic way to quickly and efficiently sample the moths flying across/through your neighbourhood. But you learn next to bugger all! This simple leaf mine has already told me so much. 

So, after all the excitement of having found Heliozela hammoniella completely new to Skye, you can probably imagine my disappointment when I realised that it has already been recorded here before. Arse. Back to the drawing board for Walkabout... 

Happily there are other members of the same moth family that haven't been found here yet. One is on oak (not a common plant up here, though there are more down south around the subtropical Costa del Armadale area) and another on Alder. Interestingly, the NBN Gateway shows a Carl Farmer record of Heliozela resplendella from Sleat area. Butterfly Conservation doesn't have that record. Rejected? Overlooked? Ignored? Who knows, but Carl is pretty good, I suspect he's correct. Either which way, I'm going to be on High Alert for Heliozela mines. A quick hour in Uig Wood turned up a blank, I shall try again. Soon as the rain stops...

Typically scrappy little Downy Birches that Heliozela hammoniella likes

Regards the title of this blog, I couldn't find anything called Hole in this Leaf, so this will have to do. From back in the day when I was three. Ah hell yeah, I remember it so well.

Hole in the Skye by Black Sabbath, early stuff for the boys yet already a masterful tune. Reckon they could go places, y'know...