By Pallab Ghosh
New research shows that when a threat comes into view fruit flies make
split-second turns reminiscent of those made by fighter jets.
High speed videos revealed the subtle wing movements that enabled them
to make the split-second “bank” turns in order to evade attack.
The study explains why other species of fly are hard to swat,
according to the research team.
The work has been published in the journal Science.
One of the researchers, Prof Michael Dickinson of Washington
University in Seattle said that the aim of the research was to learn
more about how flies process visual information.
“They process this information so quickly, as anyone who has tried to
swat a fly will have noticed,” he told BBC News.
“And they can fly like an ace at birth. It’s like putting a newborn
baby in the cockpit of a fighter aircraft and it knowing what to do.”
Prof Dickinson’s collaborator, Dr Florian Muijres, also at Washington
University, said it was “quite a mystery” how they change direction so
“These flies do a precise and fast calculation to avoid a specific
threat and they are doing it using a brain that is as small as a grain
of salt,” he said.
The researchers captured the flight of fruit flies in a purpose built
cage using three high speed cameras. They frightened the flies by
flashing up an image of a looming predator and observed closely how
the flies changed course.
What was remarkable, according to Prof Dickinson, was that the change
in wing beats was barely discernable.
“You might imagine that when a fly is doing such a crazy manoeuvre
that there would be a big change in how it flaps its wings. But it is
actually remarkably subtle. It shows the flies’ nervous system and
muscles are able to control movements to a very, very fine scale,” he
The team observed that the flies could completely change direction by
rolling their bodies and a slight flick of their wings within five
The next step is to observe what happens in the brains of the flies as
they carry out these ultra-fast changes in course.
Prof Dickinson and his team are building what is in effect a flight
simulator for flies. The insect is kept stationary but the illusion is
created that it is flying. Scientists then monitor which neurons are
activated as the flies avoid objects that suddenly appear in their
Professor Graham Taylor, who is carrying out similar research at
Oxford University, said fruit flies turn to avoid fast-approaching
objects in the same way as an aircraft – by throttling up, and
pitching or banking their body to redirect the force they produce.
“What is so remarkable is the rapidity of the response, and the
subtlety of the changes the flies make to their wing beat,” he said.
“The flies start turning away from approaching threats in half the
time it takes you to start blinking at a camera flash, and finish
throttling up their flight motor in one-fiftieth of the time it takes
you to complete the blink. It is little wonder we find them hard to
swat.” – BBC Environment