Nature on our doorsteps: Forever blowing bubbles

Many flies take in their food in a liquid form. They also sip nectar, which is made from water, sugars, and traces of proteins and salts.

After feeding, the relative proportion of water, sugars, and salts in the fly’s body can be unbalanced.

Some flies, if they need to, have a very neat way of effectively rebalancing their system.

They can reduce the volume of water in their liquid food by blowing bubbles.

By blowing their liquid food back out of their mouths in the form of a little droplet, the liquid is exposed to the air.

As the fly sucks in and blows out this droplet a number of times, water evaporates from the liquid meal, making the droplet smaller.

This fly is blowing a brown bubble to cool itself down and to concentrate the nutrients in its food

Reducing the volume of water concentrates the nutrients in the liquid food.

The smaller droplet also takes up much less space in the fly’s digestive system and so the fly can continue to feed and take in even more nutrients if it needs to.

Blowing bubbles has another added advantage for the fly. By exposing its liquid food to the air, the temperature of the droplet also drops.

When the cooler droplet is finally swallowed, it helps to cool the fly down, from the inside out.

The process of balancing water volume and body salts is called osmo-regulation.