That is the hypothesis put forward in a new research paper published in PNAS by Dr Sam England, who completed his PhD at Bristol in 2023, and Professor Daniel Robert, Professor of Bionanoscience at the University of Bristol.
Treehopper insects are known for their astonishing morphological diversity – there’s more than 3,000 species of treehoppers and they significantly vary in shape with features such as horns, spines, balls and tridents. Due to their unusual appearance, these insects have long interested naturalists, but scientists have been unable to definitively explain the function of these strange shapes. Some ideas, like camouflage, mimicry, or physical defense, make sense for specific species, but not for the whole family of treehoppers.
Based on their recent discoveries that insects like bees and caterpillars can detect static electricity, Dr England and Dr Robert wanted to test whether treehoppers extreme body shapes could help them detect static electricity.
The researchers recorded that predatory wasps emit static electricity, and also found that treehoppers would retreat from electric fields. Using computational methods, they demonstrated that the extreme morphologies of treehoppers would increase the electric field strength around the treehopper, which likely boosts their sensitivity to static electricity.
The team also found that predatory wasps carry significantly different electrostatic charges (in terms of both magnitude and polarity) from the friendly stingless bees that often protect treehoppers from predators. This could mean that treehoppers can distinguish friend from foe by electrical means alone, and provide a reason for them to have sensitive electroreception.
Dr England said: “We think our study provides a really exciting launch pad for investigating static electricity as a driver of organismal morphology more generally. 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.”
The scientists now want to probe how different treehopper morphologies could be adaptive for different electrical environments.
Dr England added: “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.”
Paper
‘Electroreception in treehoppers: How extreme morphologies can increase electrical sensitivity | PNAS’ by Sam J. England, Ryan A. Palmer, Liam J. O’Reilly, Isaac V. Chenchiah and Daniel Robert in PNAS