Treehoppers evolved weird bodies to sense electric predators

Treehoppers are tiny insects with wildly diverse shapes. Some resemble thorns, while others look like spinning tops or spikes. Over 3,000 treehopper species exist, yet the purpose behind their extreme body forms remains unclear.

A new study presents a surprising explanation. The body shapes of treehoppers might help them detect static electricity.

This fresh idea comes from Dr. Sam England and Professor Daniel Robert at the University of Bristol. The experts suggest that treehopper morphology evolved in part to sense electrical signals.

Insects can sense electric fields

Electric fields in air were once thought irrelevant to land animals. Water conducts electricity well. Air does not. But several recent discoveries changed this idea.

Bees, caterpillars, hoverflies, and even spiders can detect electric fields without touching the source.

This ability comes from hair-like sensory structures that deflect when electric forces act on them. These structures are usually setae or antennae. Treehoppers have plenty of them, especially on their dramatic pronotum.

How treehoppers detect electric signals

The pronotum is the shield-like extension on a treehopper’s back. Researchers found that it is covered with tiny, articulated setae that are likely mechanosensory.

These hairs could respond to electric fields, especially when placed at ridges and tips where the electric field is strongest.

The placement of the hair isn’t random. Shorter hairs (pit-type) sit near the base. Taller hairs (erect-type) appear at the outer tips. These positions make them well suited to catch electric signals from nearby insects.

Weird shapes make sensing easier

Using 3D computer modeling, the team found that the strange shapes of treehoppers enhance electric field detection. Sharp edges and protrusions increase the field strength near the sensory hairs.

Treehoppers with spiked or horned pronota experience electric fields up to 100 kV/m. This is far higher than those with flat shapes.

This increased exposure means they can detect other insects more effectively. Predators or mutualists approaching with a charge will create electrical signals that trigger responses.

Treehoppers react to electric signals

To test this theory, the researchers exposed treehoppers to artificial electric fields. They placed the insects on a pole and turned on a voltage source when the insect reached the top. Many treehoppers turned back, indicating they sensed something unusual.

Those that experienced an electric field were more likely to retreat than those in the control group. This behavior supports the idea that treehoppers use electroreception to detect threats.

Enemies and friends have different charges

The study compared electrostatic charges of predators and allies. Predatory wasps often carried strong, negative charges. In contrast, stingless bees known to protect treehoppers carried weaker, mostly positive charges.

This difference might let treehoppers tell allies from enemies using charge polarity and strength.

The erect-type and pit-type setae even respond differently. Pit-type hairs, for example, can detect charge polarity more reliably and from more angles.

Body shapes for electric sensing

The researchers propose that these extreme morphologies may act as electrostatic lenses. Like antennas, they draw in electric signals and improve the insect’s ability to sense its environment.

The shapes extend sensory range, increase receptor surface area, and direct electric signals more effectively to sensitive spots. This might explain why certain shapes appear more often in predator-rich environments.

Other animals may do this too

This idea may apply to other animals. Many species across insects and spiders have exaggerated shapes. If those structures also enhance electroreception, it could reshape our understanding of evolution.

“We think our study provides a really exciting launch pad for investigating static electricity as a driver of organismal morphology more generally,” said Dr. England.

“There’s plenty of other insects, spiders, and other animals and plants that also have really extreme shapes, which in many cases are currently without explanation.”

“Our study provides the first evidence of the electrostatic sense potentially driving morphological evolution, but we can’t prove this just yet.”

Treehoppers may adapt to electric cues

The next step is linking specific treehopper shapes to local electric environments. Researchers want to know if certain structures evolved to detect predators from particular angles or distances.

“If we can link treehopper shapes to certain aspects of their electrical ecology, like specific predators which approach from certain angles with particular static charges, this would really begin to strongly support our ideas around static electricity as an evolutionary driver,” noted Dr. England.

This research opens new paths. It pushes scientists to rethink why evolution created strange shapes and what hidden senses they might serve.

The study is published in the journal Proceedings of the National Academy of Sciences.

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