The great fruit-fly battle

October 29, 2022

I am at war. My enemy has overwhelming forces. Like many a conflict, my territory has been invaded in a lightening attack. In this case, by an army of fruit flies. I am battling to repel the mini squadrons, but to little avail. 

Fruit flies reproduce at an astonishing rate. Females lay hundreds of eggs on feeding sites, such as overripe fruit and vegetables. Then, within a day or the within eggs hatch into maggots, that feed on the food source. Within about a week those larvae become sexually active and not more than two days later, start the cycle over again. 

The plague has begun. I remember the exponential nature of casualties during the Covid pandemic. How did it start? For me it was a month or so ago, I suppose. I then began rudimentary measures to deprive the flies of their food store which I had identified as a bowl containing my breakfast bananas. I wrap up the bananas. No obvious loss of flies. I move the bagged bananas into the cooler. Still no noticeable improvement.

Then a coincidence. A coffee-shop companion was buying the materials for trapping the fruit flies in her own home. Her method involved preparing a concoction including apple cider vinegar placed in a jar sealed with pierced plastic wrap. The flies get in, but then succumb to their sticky fate.

I’d never heard of apple cider vinegar but drawing on my chemistry background, I figured there would be less exotic ingredients which I could use to prepare my improvised fly weapons. For example, I needed some volatile substance whose molecules  are found in rotting fruit.  

Then, an answer presents itself. I notice wine dregs in glass left out overnight. The rim is surrounded by flies in the morning. The flies detect my approach and escape. But a plan has been revealed to me.

That evening I set a trap. I Leave a wine glass laced with the intoxicating volatile vapours of Merlot on the kitchen work surface.

Early the next morning,  I prime my fly spray andI creep up, The unsuspecting enemies are surrounding the glass. A swift blast, and the skirmish is over.

New dilemmas emerge. My nightly booze is a target for attracting flies I have been swallowing unwittingly by the glug.

I m not alone in my plight. I check the situation with neighbours and find this has been a good year for fruit flies. The gold-standard weapon using Apple cider vinegar is much favoured, but with mixed results. I have won a battle, but am fully aware that the war continues.

Fun scientific fact

Fruit flies have contributed to scientific knowledge. Their rapid breeding, and relatively simple biological structures make them favoured for scientific study, contributing to our understanding of genetic processes. Six Nobel prizes have been awarded to the fruit fly scientists.

You can learn more about it in a fascinating book, First in Fly. Drosophila Research and Biological Discovery, by Harvard researcher Elizabeth Mohr.  So, it follows, we do not want to eliminate fruit flies altogether, but only to keep them out of the kitchen.

https://www.hup.harvard.edu/catalog.php?isbn=9780674971011

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