A close-up view of a fruit fly

A common fruit fly. Image: Shutterstock.com/Studiotouch

Sex, genes and boozy fruit: inside the life of a vinegar fly

Vinegar flies are some of the most important organisms on Earth. They eat a large proportion of the planet's waste, and for the last 100 years they have helped scientists to understand genetics.

Dr Erica McAlister, a fly expert at the Museum, explains how these small animals are doing great things. 

Most people think flies are little more than a nuisance. But these critters are one of the tiny organisms that keep the world turning.

They live on every continent on Earth and help maintain healthy ecosystems. Controlling pests and pollinating flowers are all in a day's work for a fly. They also provide food for many other, often much larger animals, and eat rotting waste and decomposing bodies.

Dr Erica McAlister has devoted her working life to understanding these creatures. Considering that there are about 17 million flies for every person alive on Earth, it's no small task. She explores their unique and unusual characteristics in her new book, The Secret Life of Flies.

A midge, left, and Goniurellia tridens, a Middle Eastern fruit fly, from the Museum collections

A midge, left, and Goniurellia tridens, a Middle Eastern fruit fly, from the Museum collections

 

Gardeners of the countryside

Some of the most useful species are the detritivores, which Erica calls the 'gardeners of the countryside' because they eat dead organic material.

Of these, the vinegar flies are some of the more notable. They eat a variety of plant material, but are known for their love of rotting and fermenting fruit and yeast.

Erica says, 'These flies are the alcoholics of the insect world. Both the larvae and adults are known for their love of an alcoholic drink, and can consume vast quantities of decomposing material along the way.'

Three fruit flies on a white background

Fruit flies (Drosophila melanogaster) are used for scientific research on Earth - but also in space but organisations like NASA. Image: NASA/Ames Research Center/Dominic Hart.

 

Nobel Prize darlings

This love of a tipple has come in useful to humans. Scientists have used vinegar flies in biological research for decades to help us understand genetics and inherited traits.

Drosophila melanogaster, the common vinegar fly, is a model organism for scientific research. It is so useful that eight Nobel prizes have been awarded to scientists who have used vinegar flies.

They have short life spans and breed very rapidly, making them perfect candidates for manipulating and monitoring.

Erica says, 'They are incredibly useful for research - you can get them drunk to understand how gene expression is affected by alcohol.'

Dr Erica McAlister looking at a fly specimen

Dr Erica McAlister exmaines a fly specimen from the Museum collection

 

Buzzed but useful

She also points out how similar vinegar flies are to humans when drunk. They become clumsy and fall over, become more amorous and are less able to select a suitable mate.

A study has also found that flies that are rejected by a prospective mate are more likely to turn to food containing alcohol than those that mated successfully.

Erica adds, 'Using these flies as models we can start to understand the mechanics of this behaviour. We are able to switch the flies' genes on and off and see what is specifically affected by alcohol. We can use this to understand alcoholism and related conditions.

'We can also use them to study inherited diseases and genetics, plus they were the first animal to have their genome sequenced by scientists, in 1998.'

Humans share 75% of disease-causing genes with this species. This means that vinegar flies are being used to examine neurodegenerative disorders including Parkinson's, Huntington's and Alzheimer's.

Flies would never naturally have Alzheimer's, but vinegar fly genes can be modified to bring it on. Researchers can then attempt to find ways of curing it again. And because the flies reproduce so quickly, the tests can be repeated in a matter of months.

Testing on fly genes can tell us about humans ageing, immunity, diabetes, cancer and the effects of drug abuse. You can say that vinegar flies are at the forefront of genetic research.

In light of all that, perhaps it's time we put down the fly swats. 

Buy the book

Enter a hidden world of snail killers, silly names and dangerous daily life in The Secret Life of Flies.