[This was written by Fran Siebrits and published online by Wild Magazine http://www.wildcard.co.za/, 2011]

Sight is normally responsible for stimulating sexual excitement in humans. But with certain fruit flies, it seems to be scent that acts as an aphrodisiac. 
Vinegar/wine fruit flies (Drosophila melanogaster) have sensory organs on the end of their antennae that pick up odours. Not only do these insects use their olfactory system to sniff out food, they also rely heavily on it to find a mate.

A smell of significant importance for Drosophila is one resulting from the molecule phenylacetic acid. This molecule is released by flowers, honey, fruit and other foods attractive to fruit flies. When the male fruit fly picks up on phenylacetic acid, it triggers courtship displays and mating behaviours. In other words, food smells are a turn-on for male fruit flies!

The stronger the phenylacetic odours, the easier and quicker it is for a male to start courting a female. The male fruit fly has the responsibility of tracking down females when it comes time to breed. Using their highly sensitive attenae, males are able to locate and target females that have recently been near fruit (or just fruit itself as there are bound to be other fruit flies in the vicinity).

Sound easy? Just consider the amount of other odours which can dilute phenylacetic molecules in the air. Not such a simple task after all. But evolution has played its nurturing hand again and dealt the fruit fly specialised channels which can be heightened at certain times. A complex system of calibration occurs which allows the fruit fly to distinguish between different smells.

Channels reserved for food-odours become more receptive while others are dimmed so as not to interfere. In this way fruit flies can zoom in on the tasty fruit which is so crucial to offspring when they hatch, while at the same time the scent activates the desire to mate.

And once again, the phenomenal circle of life continues.

Fruity Facts

  • There are over 1500 species of fruit fly in the genus Drosophila.
  • Males of the fruit fly genus Drosophila have the longest sperm cell of all organisms on Earth. The sperm cell of species Drosophila bifurca reaches 58mm in length. Considering that the actual fruit fly is only as small as 2-4cm, this is quite a wonder!