First New Fly of the Year

And it's not what any of us expected, especially me!

Yes it looks like a well-rotten cucumber, I agree. But this is a lifer for me! 

So you may recall that I signed up to the UK Hoverflies Larval Group on Facebook just a couple of weeks back. Well I was obviously paying attention somewhere along the line, because as soon as I found this beast glued to the underside of the boulder I'd just heaved out of the ground, I knew it was different to the usual Syrphus larvae I find in leaf litter. It seemed more wavy-edged along the margins, the colour was richer and the mottling more pronounced. But mostly, just cop a look at those rear breathing tubes! 

Cor, just look at the length of those! 

The rear breathing tubes on Syrphus are broader than they are long, these are clearly longer than broad. So, definitely not a Syrphus but what is it?

It's really quite an attractive thing, in an admittedly rather strange kind of way.

I felt that it looked good for Epistrophe, so put these three images up on the FB group. Not too much longer and it was confirmed by Nicola Garnham, one of the page admins, who said it was probably Epistrophe grossulariae but should be reared through to be certain. 

There are five species of Epistrophe in Britain, all of which occur in the southern half of England (plus one species known only from a single 'somewhat doubtful' Welsh sighting). Of these five, only two penetrate into the Scottish Highlands. One is Epistrophe eligans and the other is Epistrophe grossulariae. Happily, eligans has particularly elongated rear breathing tubes, which this larva lacks, leaving grossulariae as last man standing. All of this means that I've just ticked a hoverfly from the larval stage - I'm pretty sure I've never done that before! 

As larvae they live up in the trees feasting on aphids, particularly those found on Sycamore. The fact that I found this larva beneath a clump of Sycamore and Norway Maple makes perfect sense. They come to earth with the falling leaves, munching on any aphids that have also fallen to earth, before effectively running out of food and spending the winter in a state of dormancy. Then they pupate and emerge as adult hoverflies from April onwards (or probably June onwards up here).   

I'm also pretty sure that I ought to have seen this fly already, in the adult stage I mean. It's quite common across Britain, so is an overdue addition. I shall be keeping an eye out for the adults this summertime, I expect to be stalking and swiping at hoverflies for much of the coming season.

Syrph's Up!

Today I took a second wander up to the woods above the River Conon in search of more leaf litter lovelies. I somehow pulled my back at the end of December and it's been giving me a small degree of grief ever since. Today though, it was bad - I ended up just sitting on the ground and checking the leaves within arm's reach. Happily, I struck lucky and found a few hoverfly larvae.

This is a Syrphus, I don't know which one and I'd have to rear it through to find out. It was completely inactive, so I guess it's fully fed and settled down to pass the winter in a state of dormancy, or aestivation* hibernation as it's more properly known. Had I have thought to check the underside I probably would have seen an entirely pale belly, showing that it had voided its last meal and not eaten since. Actively feeding larvae show a dark gut-line. 

Just a few more leaf turns and I found myself looking at this fine fella, another Syrphus hoverfly

This individual showed signs of life, most notably when I dazzled it several times with the camera flash which elicited a slo-mo shake of the head and general hunching of shoulders. Yeah, I get that. I'm just the same first thing in the morning. 

I changed location, and sank awkwardly to my bum maybe fifty feet further into the trees. Bugger this! Happily, within just a few minutes I found a third Syrphus larva.

This bad boy was very definitely active, rearing up and squirming across the leaf surface. Apparently Syrphus are obligate aphid eaters, they don't have the mouthparts to successfully predate other dipteran larvae. So, quite why it was still active instead of aestivating* hibernating is anyone's guess. 

It struck me that the inactive larva was on a windswept, dry, surface leaf. The barely active larva was on a mostly dry leaf, though on the wetter underside, whilst the fully active larva was on a wet leaf. My thoughts are that the first larva will need to relocate to a more sheltered and moist site pretty soon, same with the second larva. Apparently overwintering hoverfly larvae are very sensitive to light levels, choosing to hide from brightness, and to humidity levels, avoiding desiccation by sunlight or cold winds. Presumably keeping out of the elements is also keeping out of sight for foraging Robins too, always a good move (I currently have a Robin that is hellbent on flying through my barely open window, then shitting over everything in it's panic to escape back outside. It's a repeat offender, I may have to put up some midge mesh. Anyway...)

My last post related to finding my first ever Melanostoma larva, plus the Lonchoptera larva they munch on. Today I found another favourite snack of the mighty Melanostoma

This is a Lauxiniid larva, a family of rather small flies. The outer cuticle is too tough for Syrphus (though they occasionally try it anyway) but not so for Melanostoma. And if you thought the pic was cute, just wait until you see the video clip 

If you watch cxarefully, you can see the cephalic skeleton in action as the larva feeds. This larva is approximately 3mm in length, so I'm quite pleased the camera picked up so much detail. I did briefly wonder if I could ID them to species by the shape and form of their cephalic skeleton. Turns out there are lots of them and I don't have sufficient detail in this short clip to enable a definitive ID. One for next time, maybe.  

Just because this is playing as I'm writing this, I give you The Manics and Indian Summer. Enjoy

* 'aestivation' is incorrect, see Mark's comments below for full explanation.