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.  We have just over 20 records in Highland since 2009, when we first began to take an interest in this species, and for four of these years we have no records at all.  Just S of our area, in 2011 a pair was found on Lismore.

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.  The other flies you will find indoors rarely invade your personal space.

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

NOT Musca domestica POSSIBLY Musca domestica
if the fly has ANY of the following: if the fly has ALL of the following:
  • a straight or slightly curved or sharply angled medial (discal) vein;
  • any orange on the legs;
  • eyes which touch on top of the head;
  • any distinctly blue or green colour;
  • any dark mark on the wing.
  • an obtusely curved medial (discal) 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 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.

If you think you have found Musca domestica, a specimen or good photograph will be needed for confirmation.  Other flies might be equally or even more interesting, so whatever you catch is worth identifying.
The National Biodiversity Atlas records are shown on the map above.  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) in adapting the NBN Easy Maps Widget for our needs.
Valid XHTML 1.0 Transitional