Caterpillars use their hair to detect static electricity of predators

In a recent discovery, scientists have found that caterpillars can detect their predators by sensing the static electricity they emit.

This revelation, published in the journal PNAS, highlights the remarkable sensitivity of caterpillar hairs to electric fields, particularly those matching the wingbeat frequencies of their insect predators.

What is static electricity?

Static electricity refers to the buildup of electric charge on the surface of objects. This phenomenon occurs when two materials come into contact and then separate, causing electrons to transfer from one material to the other.

One object ends up with an excess of electrons, becoming negatively charged, while the other loses electrons and becomes positively charged. These charges remain until they can discharge, often resulting in a small spark or shock.

A common example of static electricity is when you walk across a carpeted floor and then touch a metal doorknob. As you walk, your shoes rub against the carpet, transferring electrons and building up static charge on your body. When you touch the metal doorknob, the excess electrons quickly move from your body to the metal, causing a small shock.

Static electricity can also be observed in nature. Lightning is a dramatic example, where the static charge buildup between clouds or between clouds and the ground discharges as a powerful bolt of electricity.

While static electricity is often seen as a minor nuisance, it can have significant implications in various fields. In industry, static charges can cause damage to sensitive electronic components, ignite flammable substances, or affect the manufacturing processes of certain materials.

Caterpillars’ hairs detect static electric fields

Researchers at the University of Bristol have demonstrated that caterpillar hairs move in response to electric fields.

These hairs are especially attuned to the frequencies corresponding to the wingbeats of other insects, suggesting that caterpillars can detect electrical cues from their predators.

This study marks the first instance of static electricity being recognized as a sensory cue in predator-prey interactions.

“We knew that many animals naturally accumulate static electricity as they move around their environment, and that static electricity can influence other charged objects,” explained lead author Dr. Sam England.

“We wondered if a prey animal, like a caterpillar, could detect its predators by sensing the electric field they emit. Would the static charge of a predator, like a wasp, be enough to alert the caterpillar to its approach?”

Measuring static charge

The team measured the static charge of wasps and caterpillars using a static charge sensor. They used computational models to predict the strength of the electric field when a wasp approaches a caterpillar on a plant.

By observing the caterpillars’ defensive responses and employing lasers to detect tiny vibrations, they confirmed that the sensory hairs were detecting the electricity.

Impact of human activities on caterpillar sensory detection

One significant concern arising from this study is that caterpillars are also sensitive to electric fields emitted by power lines and electronic equipment. This implies that human activities may be disrupting the ability of animals to detect their predators due to increased electrical “noise.”

“It feels quite urgent now to assess whether we are hampering the ability of caterpillars and other animals to detect their predators by introducing a new type of sensory pollution – electrical noise,” said Dr. England.

Static electricity in predator-prey interactions

Predator-prey interactions are crucial drivers of evolution. Since almost all terrestrial animals, including caterpillars, accumulate static charge, this static electric sense might be widespread.

The discovery of its role in ecological interactions opens new dimensions to our understanding of animal senses and evolution.

“Our study shows that terrestrial animals can use static electricity as a predator detection cue. This ability is likely widespread, especially among insects and other small animals like spiders and scorpions,” noted Dr. England.

“This study unveils a new dimension to predator-prey interactions and hints at a previously unnoticed way in which we might be negatively impacting wildlife by introducing sources of electrical sensory pollution.”

This research not only enhances our understanding of predator-prey dynamics but also calls for a closer examination of how human activities may be affecting wildlife through the introduction of electrical noise in the environment.

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