St Mark's-fly

[ruthchmbrs]

I live in Durham, and often walk our dog through a nearby graveyard. This year, for the past week there has a been a glut of black flies hanging around, massing in open grassland where it's sunny and wind-free. They're in loose 'swarms', and don't seem to directly bother people (except that it's like walking through a wall of black snowflakes). I initially thought they were blackflies, Simuliidae (they're flies, and they're black...), but having consulted my insect guide I reckon they're St Mark's-fly (Bibio marci), as there's no water nearby, and they have characteristic hanging-down legs. I wonder why they're so numerous this year? It seems a pity that there are no swallows or house martens around, as I'm sure they'd have a feast; don't reckon other birds could take advantage unless they catch the ones that are dying off now. Interesting, anyhow.

[sunnydale]

Hi Ruth and welcome

I haven't come across any this year yet but normally encounter them while out walking towards the end of the Summer, when the Heather is in bloom.

It's awful walking through a big swarm!

Tracey

[sunnydale]

Actually Ruth, I'm getting confused with the Heather Fly! It's swarms of these that I normally see at the end of Summer.

Tracey

[Johnny81]

I would say it is Bibio marci swarms of them out at the moment.