Thursday, 11 May 2017

Lord of the Flies

Made the smallest of dents into the world of diptera today. After taking a mere 45 years to identify my first ever Gymnocheta viridis last week, today I saw three together followed by a couple of singletons and then a pair! And unlike last time I remembered to take a pic. It wasn't until later I realised there was a dirty great smudge across the lens, so most of today's pics are a bit 'soft' (ie crap). Yep, even more so than usual...

Gymnocheta viridis - really is a stunning beast of a fly!
Gymnocheta viridis is a member of the tachinid family of flies. Depending on the species involved, the female will either lay her egg in the path of a hungry caterpillar, on the outside of a hungry caterpillar or directly into the flesh of a hungry caterpillar. One way or another, once on/inside the caterpillar the egg hatches and the newborn maggot immediately sets to devouring the insides of it's unwilling host to the point of killing it. Oh, and the larger tachinids will think nothing of grabbing a beetle, rolling with it until the beetle has its legs in the air and then laying an egg in the softer underparts. Inter-species rape and death sentence all in one. Bit like the film Alien, I guess.

Here's another beauty I found sunning on a tree trunk. This is Mesembrina meridiana aka the Noon Fly. 

Yes I know it's a crap shot. It was bright, ok?
Mesembrina meridiana doesn't lay it's eggs inside unfortunate caterpillars. It's not that gross, this is a refined fly. This one lays its eggs into cow shit. The resulting maggot swims down through the sloppy gloop and basically eats any animal it comes across. It is the largest maggot of any British fly and, to the other inhabitants of the dung community, is probably the equivalent of finding a Great White Shark in your paddling pool. Nice looking fly though.

I briefly nipped into the local shop for lunch and found this fella watching me as I blitzed my way through a Mars Bar/Red Bull combo. Coz no, I'm really not sweet enough already...

Rhagio scolopaceus, known as the Downlooker Snipe Fly
These flies are sit-and-wait predators, usually adopting this characteristic resting position. From a tree trunk or fence post (or in this instance a shop wall) they dart out and grab their aerial prey. They then return to a perch and suck the insides out of their hapless victim. 

Back in the woods again I still hadn't realised my camera lens was dirty which was a tad annoying seeing as this Lucilia let me shove the camera pretty much up it's nose

"Lucilia sp" - there are several in the genus, this one flew off before I could capture it
The genus Lucilia belongs to a family of flies known as blowflies. These are the ones that seek out dead animals and lay their eggs inside the carcass. Shady and cool parts of the corpse are preferred. If ever you've spun a dead deer or rabbit (or lamb up here at the moment) and found it writhing with maggots, some of them could belong to a fly like this. 

I probably have a few of those details mixed up. I'm by no means a dipterist (someone who studies flies), but I think it's a good idea to have some level of understanding and familiarity with the background stories of the various species I encounter. It helps me place them in the grand scheme of things. 

Though sometimes ignorance is bliss - who knew flies could be so bloody disgusting!


  1. As much as the stuff about flies was really interesting Seth, the thing that really surprised me is that they have Mars Bars on Uig!

    1. Only small size though. And no Sugar Free Red Bull either. Life can be cruel sometimes.

  2. They really do have some pretty disgusting habits don't they.
    I love the noon flies,the only place I seem to see them here is at Abbotsbury Swannery where there are also plenty of Yellow Dung Flies as well, another of my favourites.

    1. They're definitely a fave of mine too. Just remember to wash your hands afterwards if you handle them and to NEVER EVER poot from a cowpat/carcass!