A “walk” is England’s best analogy for his method of tricking the insects into staying airborne for 30 seconds. “I had to tie little lassos around their waists,” he said. He leashed each flier with fishing line and coaxed them through a metal loop fixed to measure their charge.
England studied 11 species of butterflies and moths native to various climates, ecosystems, and lifestyles. After they flew around their cages for 30 seconds—enough time to accumulate electrostatic charge—he guided them through the loop. All 11 species charged up during flight. Some reached static charge of around 5 kilovolts per meter—enough to yank negatively charged pollen from 6 millimeters away, he calculated.
When lepidopterans land directly on a flower, pollen naturally sticks to their bodies. If static charge causes pollen to skip across air gaps, “it’s going to increase their efficiency as pollinators,” England said. “It makes it more likely that pollination will occur.”
To gauge static’s evolutionary significance, he looked for patterns in how the animals’ behavior in the wild correlates with their electrical charge. He found a few. For example, nocturnal moths tend to hold less charge than other species. Why? It’s possible, England speculates, that strong charges make insects more visible to predators that rely on nonvisual cues, such as static, at night. Minimizing charge could therefore help the moths survive.
“It’s great new data,” Ortega-Jiménez said. He cautioned that the study’s 11 species are a modest representation of the world’s 180,000 or so lepidopterans. “For claiming electrostatic adaptation, it needs to be more broad. But it’s a good hypothesis.”
For insects to act on static information, they must be able to detect electrical fields. Microscopic hairs on bees and spiders seem to aid in sensing, according to work from Robert’s lab. England recently expanded this unresolved science by studying how the minuscule hairs of caterpillars deflect under static, to glean how electric information may help a caterpillar survive.
When England’s team exposed caterpillars to electric fields similar to those generated by a flying wasp, caterpillars displayed defensive behaviors such as coiling, flailing, or biting. “This basically insinuates,” England said, that “prey and predator can detect each other just using static electricity.”
Dornhaus, the behavioral ecologist, questioned whether electroreception buys the caterpillar much time. Yet the high stakes of predator-prey conflict suggest that any advantage may count. “For the individual caterpillar, even just getting a small increase in the chance of surviving that encounter makes it an evolutionarily relevant behavior,” she said.