Godsold House's picture

Flat fly

Observed: 21st August 2012 By: Godsold HouseGodsold House’s reputation in InvertebratesGodsold House’s reputation in InvertebratesGodsold House’s reputation in Invertebrates
flat fly

Just over 1cm long, flat-bodied, slightly hairy with striking markings.

Species interactions

No interactions present.

Species with which a fly (Diptera) interacts


Nick Upton's picture


I should have known this belonged to my least favourite family of vile parasitic flies, though I know the larvae better... I once had a human bot fly grub picked up in Costa Rica rummaging around under my scalp for 3 weeks before a surgeon finally removed the big hairy nasty before it drilled through to my brain... (it can happen, at least in children) thought the horse bot fly goes for the guts I believe as some horrific online pics show.

Nick Upton, naturalist and photographer.

Godsold House's picture

I'm out with the fly-swat!

Thanks everyone for giving my kids nightmares! I am hoping the "horse" bit means it goes for horses...

Matt Smith's picture

Horse Bots

Yes - Horse-bots go for horses. The eggs are laid on the hairs of just above the hoof - the larvae bores under the skin and works it's way up the leg and into the body, eventually settling in the stomach. Full grown larvae are excreted in the horses droppings.

I hadn't considered a fly with fungus as the Id for this - David could well be right.

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Godsold House's picture

Horse Bots

Thanks Matt. I visited the Tachnid website and can see the level of detail required for an ID. Shame my snap this time was a quickie with a mobile phone...

Nick Upton's picture

Fat fly

Thanks Matt, I didn't realise horse bots get in that way. A very different route to how others invade: the human bot lays eggs on mosquitos and hatched larvae crawl off and burrow into us (sometimes in groups) when a mosquito visits. Check this pic out if you are feeling very strong... It brings back bad memories for me and gives me the shivers..... I could hear mine munching me and 3 successive doctors refused to believe what I told them was eating me as I knew about human bots .. I've photographed deer bot flies courting on a mountain ridge in Slovenia since and they're very nasty too, ending up en masse in the deer's throat as you probably know.

I hadn't thought of a fungal infection solution for this fly mystery either, but the wings spread posture does look like how other flies end up - I've often seen infected Dung flies swollen up on vegetation tips with the wings spread. A closer view or a crop might help to show if fungal hyphae are visible and to see the wing veins more easily to ID fly family.

Nick Upton, naturalist and photographer.

Godsold House's picture

My fly

Thanks for your interest Nick. Unfortunately my snap this time was with a mobile phone. maybe we'll never know...

Hope you're fully recovered.


Nick Upton's picture


Never mind... The bluebottle or similar with a fungus may be the most likely. Infected flies do swell up and spread their wings and look very odd. Here's one I posted: http://www.ispot.org.uk/node/272940 and another one: http://www.ispot.org.uk/node/230865 and this fungus doesn't affect us.

I'm fine now, though I do bear the scar from my not-so-little companion and now can't bear to have flies buzzing around my head!

Nick Upton, naturalist and photographer.