“The Walk” is England’s best analogy for his method of tricking insects into staying airborne for 30 seconds. “I had to tie a little lasso around their waists,” he said. He tied each flier with fishing line and pulled him through a metal loop attached to measure his load.
In England, 11 species of butterflies and moths were studied across a range of climates, ecosystems and lifestyles. After they had flown around the cages for 30 seconds – enough time to build up a unchanging charge – he guided them through the loop. All 11 species charge during flight. Some achieved a unchanging charge of around 5 kilovolts per meter – which was sufficient pull out the negatively charged pollen from a distance of 6 millimeters – he calculated.
When lepidoptera land directly on a flower, the pollen naturally sticks to their bodies. If the unchanging charge causes pollen to jump through air gaps, “it will increase their effectiveness as pollinators,” England said. “This increases the likelihood of pollination.”
To assess the evolutionary importance of electrostatic charges, he looked for patterns in which animals’ behavior in the wild correlated with their electrical charge. He found some. For example, nocturnal moths tend to have a lighter load than other species. Why? It’s possible, England speculates, that the sturdy charges make the insects more noticeable to predators that rely on non-visual cues such as unchanging interference at night. Minimizing the load can therefore lend a hand moths survive.
“This is great new data,” Ortega-Jiménez said. He cautioned that the 11 species included in the study are a modest representation of the approximately 180,000 lepidoptera in the world. “In order to claim that this is an electrostatic adaptation, a broader consideration needs to be taken into account. But it’s a good hypothesis.
For insects to act on static information, they must be able to detect electric fields. Research in Robert’s lab has shown that the microscopic hairs of bees and spiders aid in sensing. England recently extended this previously unsolved science by examining how tiny caterpillar hairs bend under the influence of electrostatic charges to discover how electrical information can help the caterpillar survive.
When the England team exposed the caterpillars to electric fields similar to those produced by a flying wasp, the caterpillars showed defensive behavior such as curling, flailing or biting. “This basically suggests,” England said, “that prey and predator can detect each other using static electricity alone.”
Dornhaus, a behavioral ecologist, wondered whether electroreception gave the caterpillar a lot of time. But the high stakes of predator-prey conflict suggest that every advantage can count. “For a single caterpillar, even a small increase in the odds of surviving this encounter makes it an evolutionarily significant behavior,” she said.