How and why would flies get into ointments?
Entomologist Richard Jones demystifies a well-known saying.
Today, ointments come in sterile pots and tubes, the active pharmaceutical ingredient mixed with an oily carrying agent. These are unattractive to insects, and may even contain other chemicals to kill micro-organisms, bacteria and fungi.
The expression ‘a fly in the ointment’, meaning a small thing that ruins all, is likely from the Bible, a time when ointments would have been brewed from all manner of natural unctions including tallow (rendered animal fat), vegetable oils and beeswax.
Unlike inert modern synthetic bases, these would have had a ripe aroma from the start, attracting plenty of curious insects (all referred to then as 'flies').
Animal fat ointments would entice blowflies and tiny carrion beetles, which would mistake the medication for the putrescent stage of carrion decay. Plant concoctions could resemble fermenting sap, crushed leaves or decaying fruit, bringing in houseflies, fruitflies, fungus gnats and even hoverflies and bark beetles. Beeswax, and the heavy complex scent of the hive, would be a major draw to wax moths, wasps, hornets and bees.
Richard is an entomologist and writer. After a semi-feral childhood spent exploring the South Downs and Sussex Weald he now lives in south-east London. He is a fellow of the Royal Entomological Society and a past president of the British Entomological and Natural History Society. As well as contributing to Countryfile, he also regularly writes for BBC Wildlife, New Scientist, The Guardian, Sunday Times. His latest books include Mosquito and Wasp in the acclaimed Reaktion Books Animal Series, Call of Nature: the secret life of dung, Beetles in the HarperCollins New Naturalist Library, A Natural History of Insects in 100 Limericks, and Ants in the Bloomsbury British Wildlife Collection. There are entomological musings on his blog at www.bugmanjones.com
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