Ask The Entomologist

Shiny flies

Earlier this week we visited Trego School, to see the results of the salmon snagging fieldtrip. After the fish were had been cleaned and packed away for children to take home, I saw many bluebottle and greenbottle flies, as well as a few paper wasps, flying about outside of the school, sucking up fish juices.

Bluebottle and greenbottle flies are blowflies, members of family Calliphoridae, a name which translates to “carriers of beauty”. Rather fitting, given their bright metallic hues. Additionally, adult blowflies are excellent pollinators, and a very good thing to have in your garden.

Two greenbottle flies, genus Lucilia, contemplating romance over a salmon dinner.

Blowflies have an incredible sense of smell. In most parts of the world, blowflies find bodies within minutes of death, detecting the first smells of decay long before humans are able to. When they find the right sort of decay (some blowflies prefer dung to death), blowflies quickly mate and lay eggs before flying off.

People throughout ancient Greece and Egypt believed that these shiny flies were the souls of the dead. Even today, some people in those countries consider it bad luck to swat at them, for fear that you might kill someone’s ancestor. I think this is a particularly beautiful story.

Imagine, sitting gathered with family and friends as a loved one passes on, breathes their last breath. Within minutes, you can see their soul, in the form of a beautiful fly, flying about their mouth, nose, and eyes. Almost as if the soul is sorry to leave the body, as if the person wants to stay with their family. Perhaps they say “goodbye” before flying off to the afterlife.

Today blowflies are appreciated for more than their attractive colors and spiritual significance. They are the most useful insects in forensic investigations – their young are very useful for figuring out time (and sometimes place) of death. While other insects can be used, blowflies are a forensic detective’s best friend.

Blowfly maggots have even been used in medicine, as a way to clean dead flesh out of wounds, preventing sepsis and gangrene. Medical maggot use predates antibiotics! Napoleon’s surgeons noticed that fly maggots increased soldier survival! In the American Civil War, both sides used blowfly maggots to clean deep wounds. Maggots continued to serve and save lives in World Wars I & II, and are used for some conditions even today.

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