Houseflies spread disease by traipsing dung all over our food.
Despite an immense and varied industry devoted to protecting us from the deadly housefly, the fact is that if you live in Britain, your precautions are probably unnecessary. There are two kinds of housefly: Musca domestica and Fannia canicularis. Musca is no longer common in the UK, except in rural areas where there are plenty of manure heaps in which it can breed. It used to be our main housefly, and is indeed a notorious spreader of a wide range of pathogens, but its sad decline began when motor vehicles started to replace horses: cars don’t crap. In most of the UK, the muscid you’re likely to encounter is Fannia. This is the fellow seen flying triangular patterns underneath hanging lightbulbs, and is not linked with disease, having, unlike its cousin, no interest in human food.
BBC Wildlife magazine, Nov 2009; correspondence with Dr Peter C Barnard, Director of Science at The Royal Entomological Society.
If you happen to be in a country still hymned for its bucolic charms – such as France – please note that M. domestica continues its dirty work in such places with never-dimmed enthusiasm. If your data clashes with ours, you’re invited to rub your legs all over FT’s letters pages.