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ENTM News: Fruit flies, geneticists and homeowners

Fruit flies, geneticists and homeowners

​Tom Turpin
On Six Legs
August 22, 2013

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Geneticists call these little flies Drosophila. Most people know such insects as fruit flies, or possibly vinegar flies or pomace flies. Scientists consider one species of these flies to be a valuable research animal. To the majority of folks, though, a fruit fly is just a pest insect.

 
There are a lot of species of fruit flies - some say as many as 15,000 - and a lot of them are common insects. One with the genus and species name of Drosophila melanogaster has been a model research animal for geneticists for many years. Research on this insect is the basis for much of our understanding of genetics.
 
Drosophila melanogaster and other fruit flies are classified in the family Drosophilidae, or at least they have been for many years. Recently, scientists using modern DNA analysis techniques have discovered that Drosophila melanogaster should really be renamed Sophophora melanogaster. Some scientists have suggested we should suspend the rules used to change scientific names and keep the name Drosophila melanogaster. After all, this is one scientific name that many people outside of the scientific community recognize.
 
The common names of these flies tell us something about where they are often encountered. Fruit flies because they are around ripening fruit. Vinegar flies because they are attracted to fermenting plant material. Pomace flies because they are associated with the residue that remains after crushing fruits to make cider or wine. In fact, the English poet John Milton captured the relationship of this insect to both crushed fruit and fermentation in "Paradise Regained" with the lines:
 
"Or as a swarm of flies in vintage time,
About the wine press where sweet must is poured" 
 
One reason why fruit flies are good animals for genetic studies is that they have a short life cycle. It takes about 14 days to complete a generation of fruit flies at about 80 degrees F. That means that at summer temperatures, a fruit fly spends about a day as an egg, seven days as a larva, four days as a pupa and two days as an adult, before it begins to deposit eggs. The female can live for up to a month and deposit more than 500 eggs.
 
Another reason for the use of fruit flies as laboratory animals is that they readily feed as larvae on a variety of agar-based artificial diets, which are convenient to produce. In addition many individuals can develop on a limited amount of food.
 
The same reasons that fruit flies make good research animals - short life cycles, small size, a variety of food sources - plus the fact they are widespread in the wild mean that these insects can sometimes be troublesome to humans. Fruit flies do not sting or bite and do not carry human diseases. Nonetheless, having a number of these little insects flying around in the kitchen is something most people find annoying.
 
Fruit fly encounters become more frequent during late summer and early fall, when decaying fruit material outdoors provides great development sites for larvae. Home infestations develop when fruit flies find their way into a dwelling. In addition, fruit in the home, especially if damaged or overripe, could be infested with fruit fly larvae that will become flies.
 
So what should you do to get rid of unwanted fruit flies in your kitchen? First, eliminate any fruits or fruit residue that might serve as a development site for larvae. Think about those peaches, bananas or tomatoes just sitting on the counter. Or peelings tossed into the garbage.
 
If flies are present, using a fly swatter is one approach. Another is to attract the flies into a trap. Such traps can be purchased, or you can make your own. Put a little vinegar in a jar and fashion a funnel to the top. The flies, attracted by the vinegar, will find their way into the jar.
 
Another possibility is what my grandmother did. Place an overripe banana or tomato in a bowl and leave it out overnight. In the morning, quickly cover the bowl with a cloth. The flies that have been attracted to the fruit are now captured under the cloth. Then, you have a decision to make. You can capture and release: Take the covered bowl outside. Or you can capture and destroy: Putting the covered dish in the freezer works well!