(Paris) Butterflies not only covet flower nectar, but can also help pollinate flowers by storing a static electric charge while flying, according to a study published Wednesday.
Lepidoptera, that is, butterflies and moths, are among the pollinating insects, carrying pollen from one flowering plant to another for reproduction.
A role that has been minimized by certain studies that have made it above all a “parasite”, more thirsty for nectar than anything else, notes biologist Sam England, at the German Leibniz Institute for Evolutionary Science and Biodiversity.
The study he signed in the journal Interface from the British Royal Society is the first to measure their pollination capacity using the electricity that the animal charges itself with while flying.
Major pollinators, such as bumblebees and honeybees, have long been known to collect pollen and release it through contact with the reproductive organs of flowers.
It was only in the 1980s that biologists assumed that electrostatic forces could also play a role in this process, which is essential for the sexual reproduction of flowering plants.
“It’s something that hasn’t been explored in detail in ecology,” says Sam England.
The idea is that when flying, the insect’s body accumulates a positive electrical charge, produced by the friction of the wings with the air. However, “a good proportion of flower pollen is negatively charged,” continues the biologist.
Opposite charges attracting, this pollen would naturally be directed towards the abdomen of the pollinating insect. It would then take on a positive charge during its transport to another flower. Where it would naturally be attracted to the negative electric field of this flower.
“Contactless” pollination
“It has been shown that bees accumulate significant electrical charges in this way,” he said, but “no one had quantified this for butterflies.”
For his study, taken from his doctoral thesis at the University of Bristol in the UK, Sam England measured the net electrical charge of eleven species of butterflies, native to five continents. Using in particular a picoammeter – an instrument measuring tiny electrical charges –, placed at the exit of a tunnel in which each butterfly flew for at least 30 seconds.
Result: “most of the lepidoptera accumulated a positive electric charge” according to the researcher, who then used digital simulation software to model the electric field established between the insect and the flower, as well as its action on the pollen.
The study concludes that on average, the insect’s electrical charge provides enough electrostatic force to lift about a hundred pollen grains 6 millimeters high in less than a second, up to the butterfly’s abdomen.
All of this results in “contactless” pollination between the flower and the insect.
The study found that the carrying capacity of butterflies varied significantly between species. The researcher speculates that this has something to do with evolutionary pressure. “It’s speculation at this point, but there are correlations with different ecological factors,” England said.
“Some animals might find it beneficial to be good pollinators,” with a high electrical charge, “because that would mean there would be more plants for them to feed on.”
Conversely, others might benefit from carrying a lower electrical charge. Because the accumulation of pollen could slow them down, and make them more vulnerable to attacks by predators.
“It has also recently been discovered that animals can detect other animals thanks to the electric charge they carry,” as with caterpillars which are thus warned of the proximity of a wasp.
The goal would then be for certain insects to be “electrically invisible or camouflaged,” imagines the researcher.