Summer challenge 2017
The House-fly Musca domestica

Ask most people if they have seen a House-fly Musca domestica and they will tell you their kitchens are full of them.  Sadly or otherwise, the true House-fly is very scarce in Britain these days, and very few flies in houses are indeed House-flies. Recent records from Highland were in Inverness in 2009 and 2010; near Edderton, at Strathpeffer, and on Raasay in 2015; and in 2016, Rosemarkie and Nethy Bridge were added.  Just S of our area, in 2011 a pair was found on Lismore.  The map below shows records on the NBN Atlas since 1990.

One useful clue is that House-flies, unlike other flies in houses, are a particular pest at mealtimes, darting about your person and the food you are trying to eat.  If you meet a fly behaving like that, even in a respectable home or hostelry, bottle it and send it in.

House-flies are quite tricky to recognise, but it is easy to eliminate many common flies from consideration.

NOT Musca domestica POSSIBLY Musca domestica
  • a straight or slightly curved or sharply angled medial vein;
  • any orange on the legs;
  • eyes which touch on top of the head;
  • any distinctly blue or green colour.
  • a sharply curved medial vein (arrowed in the image below);
  • four pale dusted stripes on the thorax;
  • some orange on the sides of the abdomen;
  • length around 5-7mm.
Musca domestica wing

Photo © Malcom Storey (arrow added), source.
Many of the images of 'house-flies' on the web, some even on what should be trustworthy sites, are wrongly identified, so caveat emptor if you surf for additional information.  A number of reliable images are on the excellent Diptera.info site starting here.

The House-fly is associated with humans all over the world, feeding and breeding in faeces and other organic waste.  It is a vector for many serious pathogens.  It seems to have declined markedly in Britain with improvements in sanitation and waste handling, and may best be sought around farmyards where livestock is kept, rather than indoors.

If you think you have found Musca domestica, a specimen will be needed for confirmation.  Other flies might be equally or even more interesting, so whatever you catch is worth identifying.
The National Biodiversity Network records are shown on the map above. (See terms and conditions). Data providers and the NBN Trust bear no responsibility for any further analysis or interpretation of the information in the maps. We acknowledge the help of Jim Bacon (CEH) and Duncan Rowland (NBN) in adapting the NBN Easy Maps Widget for our needs.
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