Sunday, January 20, 2008

Do fruit flies like coffee?
Or, Technology in daily life: a short story

So the last couple of months, our kitchen has been plagued by fruit flies.

The infestation started in late summer, no doubt originally attracted through our screens by the bananas that my wife routinely allows to turn brown before turning them into banana bread, which is in turn rapidly devoured by our kids.

....turns into....

Fruit flies love browning bananas too. The females lay their eggs on overripe fruit; the eggs hatch in 24 to 30 hours, the larvae feed on the fruit, for five or six days, then pupate, then emerge as adults who, within 48 hours are copulating with other fruit flies to produce more eggs, etc. The whole cycle takes about 8 to 15 days "depending on the temperature" (source).

So really there are only a few ways to get rid of a fruit fly infestation. You can (a) remove all of their food, (b) lower the temperature so the adults can't survive, (c) reduce their sex drive, or (d) kill all of the adults.

So, of course, we tried (a) first. The nearly-rotten bananas were removed to a ziploc bag in the feezer. The fruit flies moved to hovering around the aloe-vera-containing soap by the sink. The soap container went into the refrigerator. Oddly, the flies began hanging out near the coffee grinder. (Fruit flies seem to really like coffee!) The coffee grinder got cleaned and put away. Still, fruit flies everywhere.

So we thought about option (b). Normally, fruit flies disappear from the out-of-doors when autumn's frost comes. So, theoretically, we could induce frost in our apartment, and get rid of the flies. (But see this article, which clearly indicates that 100% mortality requires either many repeated frosts, or it has to be below -5°C). After considering the collateral damage that might occur in our apartment (including possible frozen pipes and stressed-out people), we decided option (b) wouldn't work for us.

Option (c) is simply not possible.....fruit flies LOVE sex nearly as much as they love rotting bananas. So that one was out too.

So option (d) remained. My daughter decided that she could eliminate the fruit fly infestation single-handedly by chasing each of the adults down and (well, double-handedly) suddenly crushing them skillfully between her clapping hands. For weeks, she practiced this martial art on the poor flies, scattering carcasses around the kitchen and, eventually, getting very good at it and coming to the conclusion that the flies are "incredibly stupid" and can be easily killed. However, the fruit flies don't NEED to be smart...they have something incredibly more valuable in the scheme of things: prolificacy! The fruit flies endured, seeming to relish the opportunity to match my daughter's increasingly deadly (and increasingly regularly-heard) clapping by simply having more sex and producing more new fruit flies.

So we needed a more efficient way to kill the adults. My daughter had to go to school, after all, and occasionally leave the kitchen to sleep or use the bathroom. We needed a killer with not only determination but "staying" power.

We asked everyone we know if they knew how to end a fruit fly infestation. The option of "bombing" our kitchen with insecticide was appealing for its likely quick effectiveness, but we didn't like the idea of covering all the stuff in our kitchen with poison. My wife and daughter made a trap by laying a bit of rotting banana in a plastic container, the lid nearby ready to trap the flies...but they were too random to all alight at once on the bait. One friend suggested a "natural" fruit fly insecticide ("you can probably find it on the internet"), but we couldn't locate what she was talking about.

Finally, intrigued by the surprising affinity our (we were getting a little possessive of our little colony) fruit flies had for the coffee grinder, I spent a little time trying to find out if fruit flies eat coffee. Naturally, being a bit of a computer geek, I used Google. I typed "fruit flies coffee" into the search bar, and began browsing the hits.

While I never actually answered that question (do they like coffee? Anyone know?), I found this blog post on the "coffee monologues" blog that suggested a more efficient trap for fruit flies than our open plastic container.

I emailed this link to my wife and daughter, hoping they might take the suggestion and build a better fly trap.

But I still wanted to know if fruit flies like coffee. Maybe eating coffee grinds increases their sex drive, I thought. So I looked further down on the hit list and found this intriguing title:

Recently, I noticed small fruit flies around my coffee maker. Why?!?

I figured THAT page would answer my question for sure. So I went to the page (; yes, I'm not above using BOTH Google and Yahoo in one fact-finding mission), but alas, no answer to the fruit fly/coffee maker connection! However, there was the "best answer - chosen by voters" -- "a good clean kitchen is the best defense against these guys!" Duh! But that hadn't worked for us (maybe we aren't "clean" enough???!?). I needed a better answer!

About to give up my search, I just happened to notice that below the "best answer - chosen by voters" was a section labeled "Other Answers." So I scrolled down, and the second answer, posted by Fair_Fun, was a piece of user-contributed text that is worth its weight in gold. (I love you, Fair_Fun!!!)

I don't know why they would be around the coffee pot or how to keep them from coming back BUT,

it started, much to my chagrin (I STILL don't know why the fruit flies were hanging out near the coffee grinder), then continued:

to get red of fruit flies , take a small glass (I use a shot glass) and fill half way with apple cider Vinegar and 2 drops of dishwashing liquid and mix well. You will find those flies drawn to the cup and gone forever.

Hmmmm, I intriguing idea. Clearly the fruit flies (these might have been "vinegar fruit flies"...vinegar is, after all, one of the products of rotting [fermenting] fruit... and apple cider vinegar would probably attract them. But why the "2 drops of dishwashing liquid" and exactly HOW would they be "gone forever"?!?

Well, I emailed this new answer to the wife and daughter, and spent the rest of the day thinking about this "solution," and realized that the dishwashing liquid had one of two possible purposes. It could be the "poison" that would kill the little buggers or......perhaps more perniciously, maybe the soap would reduce the surface tension on the vinegar, and when the fruit flies landed on the vinegar, expecting to take a sip of the luscious liquid and fly off again, they would SINK, unable to extract themselves, and would DROWN, never to buzz around our coffee grinder again!!!

By the time I got home, I was ready. We didn't have any apple cider vinegar at home, unfortunately, but my wife was stopping at the grocery store the next day, and I quickly added this to her list. When she got home the next day, I anxiously found the bottle....

....(Hmmmm, I thought, how ironic, using "organic" vinegar to attract fruit flies in order to KILL them!!!), found my daughter to help and observe, and we filled a shot glass about 2/3 full of vinegar, added a couple of drops of dishwashing soap, and placed the shot glass above the sink. Immediately we noticed a few fruit flies hovering around the shot glass. Immediately after THAT, we noticed the pungent smell ourselves, which we would be living with for the next few days. A courageous fly landed on the edge of the shot glass, we waited, off he flew again, startled by our hovering we left, down the hall, to let the concoction do its thang.

In a few minutes, I went back to the kitchen, and noticed one fruit fly frantically struggling to free itself from the surface of the liquid. I thought, awww, poor fruit fly, what a way to go, then maliciously rubbed my hands together at the thought of the whole colony following in his pitiable path. A few hours later, we found about 10 fruit fly carcasses at the bottom of the glass. The next day, about 30. The next day, one lone fruit fly hovered near the coffee maker, 45 or so of his colleagues nearly covering the bottom of the shot glass.

The next day, I didn't think about fruit flies, for the first time in months, although I did continue to notice the strong smell of vinegar near the kitchen sink. The next day, I didn't even notice that. Finally, the day after that, I realized I wasn't thinking about fruit flies any more...the obsession gone, along with the pesky creatures themselves.

The experiment had worked! The entire fruit fly colony, floating languidly at the bottom of our vinegar-dish soap solution, unable to propogate, unable to buzz annoyingly across our fields of view, gone, we hope, until next spring, when they might return, if my wife insists on letting those bananas rot, and if we don't decide to put little glasses of vinegar and soap solution all over the house.

Which, I wonder, is worse...the constant smell of vinegar in the kitchen, or those persistent little flies, carrying out their natural duties in the friendly confines of our kitchen?

As I write this final sentence.....

....across my field of view....

...flying from the plants in the window of my home office....

....ARRRGHHH!!! It's a fruit fly!!!!

Where IS that bottle of vinegar?


Joel Galbraith said...

great story. Loved it.
-Joel G.

august said...

Hell ya, I hate reading but this was interesting.

august said...

Hell ya, I hate reading but this was interesting.

AngelK said...

wew... I found this article when I was trying to find answer of my flies like coffee?

Why asking that? Several times I found a dead fly in a cup of black coffee. It was really annoying for me since I had to throw away the coffee and made the new one. Why always in my coffee? not my hubby's tea? Those questions got me to find the answer.

Anony said...

This might complete part of the story for you: I had a fruit fly infestation after I let a bunch of bananas rot in a bowl, and they just wouldn't go away, though I got rid of every non-frozen or non-refrigerated food item.

I have a bad habit of making my coffee in the dark in the morning and running out the door for the day without cleaning out the press, since I'm always short on time. I'll clean the press the next morning, but usually just by rinsing it out in the morning - and then I throw some boiling water and grounds in and repeat, all in the dark.

Tonight I looked in my French press, after having left it for a day or two. There were fruit fly maggots crawling in the leftover grounds. I can't even begin to tell you how utterly grossed out I am, but I thought it might help you to tell you that wet coffee grounds can definitely breed fruit flies.

sugar said...

yes they breed in wet groung coffee. i am now drinking instant as pay back

snailpaw said...

Ha! I found this after googling "fruit fly larvae in coffee". I kept finding tiny, tiny (barely noticeable) creatures wriggling about in my coffee pot about an hour or two after brewing. It's begun to drive me nuts, because I hate wasting coffee! I'm not sure of the reason why, but it seems that fruit flies love sexin' in the coffee. Hmph.
Thanks for the vinegar/dish soap tip!