Sunday, 6 January 2019

It's a Fly-Eat-Fly World out there...

Firstly, I have to apologise for today's large cross-over in content between this blog and that of my Skye Inverts Blog. If you follow Skye Inverts you'll probably recognise most of these images and names. Sorry 'bout that. But this isn't a feeble cop out, pan-species listing encompasses the beetles, flies and bugs that the other blog is wholly devoted to. There's bound to be a bit of overlap. However, today was special (for me) so you get two versions of the same events. I'll try not to let it happen again too often, honest guv. 

Today was just great! I went out and undertook a deliberate search for something that I've only very casually encountered beforehand, something that I have very little understanding or knowledge of, something that I have, quite literally, been walking all over for years - yep, you've guessed it in one, free-living, winter-active fly larvae. Well done you! Note that I don't call them 'maggots', in fact that's the only time I shall be using that word in this blog. There's a reason for that. 

So two days ago I stumbled across the snazzily named UK Hoverflies Larval Group's Facebook page and immediately asked to join. They let me in - huzzah! I spent the next 15mins scrolling up and down the screen, familiarising myself with what the various winter-active hoverfly larvae look like, and today I set off into them thar hills to find me some maggots dipterous larvae.

I started by finding lots of these small, semi-transparent worms on the underside of wet leaves

One of the Pot Worms (family Enchytraeidae)
I tried to do a little research into these, but it very quickly became overly technical and scary. I think there are probably quite a few of them and that you'd need a scanning electron microscope and an advanced DNA kit to progress very far. They're pretty common between wet leaves that are stuck together, go check for yourself. 

The next commonest beast I found amongst the leaf litter were these things

A Tipulid larva (cranefly family)
I found these sometimes two or three to a leaf, all about 8-10mm long, all brown and all having possibly the best feature on any animal out there!

LOOK! It's got a funny face for a bum!!!!!!!
I couldn't believe it when I first noticed this, and in real life it's just so much better! I'm going to go back and grab a whole bunch of them, bring them back indoors and photograph their bums properly. I might end up making a calendar of cranefly bum characters and sell it off to Pixar or Marvel for a bomb. This time next year, Rodney, we'll be millionaires!  

Despite having far too much childish fun with the anal spiracles of cranefly larvae, I hadn't yet found what I'd come out looking for. Happily, that soon changed. 

A hoverfly larva from the genus Melanostoma 
What a distinctive beast that is!
As far as I can tell, this represents the first ever example of my targeting a free-living (as opposed to leaf-mining) fly larva and actually finding it. I've stumbled across hoverfly larvae before, but only occasionally and only by accident. Never planned, never searched for. I was pretty damned chuffed! But there was more...

It's a fish! No, a crustacean! It's an isopod! Trilobite? The heck is it???
I find these tiny (2-4mm) "things" quite infrequently. Today I found maybe ten of them. Which is probably as many as I've ever seen before. I knew it was a fly larva, I've Googled them before, but I couldn't remember the family. Turns out to be a lonchopterid in the genus Lonchoptera. There are only six species in Britain and Ireland but you need to rear them through to adulthood in order to identify them. Personally I reckon they must be doable as larvae too, but I haven't found that key yet. 

Lonchoptera larvae are snack-sized prey items for Melanostoma larvae, which flip them on their back and stab them through the belly before sucking out the body fluids. Nice... However, Melanostoma isn't quite the king of the jungle around here, for this Bad Boy will happily devour any Melanostoma it encounters

Phaonia sp (Muscidae) - the Great White Shark of this blogpost
The Lonchoptera larva above was about 3mm in length. The Melanostoma larva was about 8mm. This larval Phaonia was about 10mm. Again, it needs to be reared to adulthood before being identifiable to species, but it was still great to find and observe - prowling its way across wet leaf tissue, ready to tear into anything small enough to get in its way. Geoff Wilkinson on the FB Group identified this beast for me, he also warned me to keep it away from anything else I wanted to rear through as it would simply devour them. 

However, I didn't retain any of these larvae to rear through. It's an awful long way until springtime happens up here, probably at least another four months. There's no way I could keep these incredible beasts alive and well for all of that time. 

Today's enjoyment has been discovering what was, for me, a hidden world. Hidden in full view, as it happens. Searching for, and successfully finding, these fly larvae buried away from casual sight deep in wet leaf litter has been a real eye-opener for me. A small peep through the curtain into a very different world. Quietly feeding, hunting and being hunted - pick axed apart by voracious, unfeeling predators, innards mashed up and body cavity sucked dry, the survivors transforming into those familiar buzzing insects we are so used to seeing in flowerheads or sunning on tree trunks and brick walls. Little have I thought about, or appreciated, the lifestyles some of these flies lead before becoming adults. I'm starting to see them in a different light, starting to understand their lifestyles, fleshing out the bald names with colourful information. 

I was never really sure how I'd progress with flies. I find the anatomy of the adults quite fascinating, the sexual dimorphisms, the awesome body musculature, the vast array of bristles (why, what purpose do they serve?) but now I'm seeing the larval stages as entities in their own rights too. I doubt I'll ever be more than a half-baked dipterist at best, but in truth that's already an entire level beyond what I thought I'd ever achieve at the start of this year. Flies, I have discovered, are very bloody cool. And they may be slowly snaring me...

Damn, but this is an excellent tune! 


  1. Huzzah! Welcome aboard. You do have the free downloadable key to hoverfly larvae right? Did you know Beelzebub means"Lord of the Flies"? Also don't forget (because I often do) that the Soldierfly book has larval keys. Excited about this new direction. I may try to find way to get up and do some inverting (inversion?) in Skye this year

    1. Do it, just tell me when's best for you! I didn't know about the "Lord of the Flies" bit, no. So, David Gibbs (well over 3K flies in Britain) has a new nickname? ;)