Fruit flies feast on fermentation
By: Susan Jones
| Posted: Saturday, Sep 01, 2012 06:00 am
Oh boy! It’s that fruit-fly time of the year again! Of course, it’s fruit-fly season in the spring too and if you eat a lot of bananas, or mangoes, why you can have these jim-dandy little critters as house pets all year long.
Fruit flies, which go by the Latin name of Drosophila melanogaster, will happily make themselves at home anywhere there is rotting or fermenting or composting fruit. Walk down most established St. Albert streets this time of year and you will smell apples and sour cherries and even decaying saskatoon berries. Go into any St. Albert kitchen and you’ll find a pretty little green-lidded composter bucket. All those things are a great attraction for the tiny fruit fly.
“I cannot tell you whether they are local fruit flies because the domestic fruit fly, the one you have in your kitchen, is all over the world,” said Peter Heule, life sciences technician at the Royal Alberta Museum.
Heule admitted he too is finding the flies a nuisance in his own home this year.
“I’m quite fed up with them. There are clouds of them around the garbage, which, because of recycling, only goes out about once a week. I’ve developed this catching technique of clapping one hand against the other because you cannot grab them with an open palm,” he said, adding that the simplest method of getting rid of the flies may be to put the composting garbage outside the back door.
Fruit flies have huge eyes and they can easily see you. The more you swat and grab at them the more practice the flies get at dodging.
“They cannot see detail. They can’t see your face but they see you swatting at them all right,” said Heule.
Compared to other species, fruit flies reproduce very quickly, and while that makes them more of a nuisance in the kitchen, geneticists love them.
“They have allowed us a greater understanding of genealogy because they reproduce so quickly. Within a few generations you can study the changes and mutations. Scientists even study the different mutants, the messed up ones, with antenna where they should have legs. We owe most of our understanding of genetics to fruit flies,” he said.
Heule purposely cultivates fruit flies at the Royal Alberta Museum and uses them to feed some of the tiny spiders located in the Bug Room.
“The tiny black widows eat them,” he said.
He saves banana skins, pineapple and mangoes to attract the flies but he also finds this performance somewhat ironic.
“For a while we had too many fruit flies and they were hard to get out of the lab so I got a fruit-fly trap at Lee Valley and it worked very well. Now I’m trying to cultivate them and using a vacuum to catch them,” he said.
A brownish banana will have an alcohol content of five or six per cent, which is too high for some insects to manage. Heule explained that fruit flies have adapted to the high alcohol content and even use it as a defence mechanism against parasitic wasps.
“The parasitic wasps are tiny and they lay eggs on the other insects. But the alcoholic content of the fermenting banana is too high for them so they bale out, leaving the fruit flies to eat the fruit and lay their own eggs on the fruit. The flies aren’t so much interested in eating the fruit. They are interested in laying their eggs. They are doing the best parenting they can by laying their eggs on the fruit or, better yet, in the kitchen garbage,” he said.
It’s nice of the fruit flies to want to get rid of all that fermenting fruit for us. But not in my house, not in Heule’s house and likely not in yours either. Short of walking around blindly grasping at air, the best method of eradication is to attract them with vinegar.
“The Lee Valley traps are inexpensive and they use vinegar. You could make a trap yourself using vinegar, and the fruitier the vinegar is, the more it will attract the flies,” Heule said.
A simple trap could be a funnel-like structure on top of a bottle that has a little vinegar on the bottom of it. The flies crawl in but cannot get out again. A little vinegar in a pill bottle will also work if you poke small holes in the lid.
Fruit flies will also be attracted to the bathroom because they are thirsty so put a few traps in different locations in the house. The more traps you have the more flies you’ll catch.