New scientific discovery
Caterpillars have a sixth sense that most land-based animals do not.
They can sense electric fields around them with small bristles called setae on its body — a feat called electroreception.
British researchers have discovered this in laboratory experiments and their findings were published recently in the Proceedings of the National Academy of Sciences.
They studied four species of caterpillars: cinnabar moth, scarce vapourer moth, European peacock butterfly, and common wasp.
Ability to sense electric fields using tiny hairs on their bodies
As an insect’s wings flap through the air, static charges build up on them.
When it nears the caterpillar, the setae sense these charges by building up charges of its own.
This mutual interaction gives rise to an oscillating electric field.
How it helps it from predators
In the study, researchers stimulated caterpillars with a live electrode carrying a voltage oscillating at 180 Hz, to mimic an approaching wasp
The caterpillars’ setae responded to frequencies of 50-350 Hz, possibly to help distinguish between threats and non-threats
The setae vibrated the most when the field frequency was 220.3 Hz — close to the rate at which many predator insects flap their wings.
Caterpillars could have evolved to tune to their predator’s wingbeats.
These animals have had a lot of evolutionary pressure upon them to evolve defences because so many animals like to eat them.
Caterpillars don’t rely on electroreception alone to sense predators
It supplements the other five senses.
“Sensory pollution” could damp the caterpillars’ electroreception.
The setae are sensitive to voltage frequencies also present in overhead power cables, around 50-60 Hz.
This ‘exposure’ could desensitise the setae and diminish the caterpillars’ ability to spot predators with them.
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