A pollinator can read a flower’s color, shape, scent and even its temperature, and bumblebees are known to add one more channel: the electric field around the bloom. Hoverflies are major pollinators in their own right, and nobody had asked the same of them. Khan and colleagues measured how a hoverfly picks up charge and how a floral field varies. Is there a fifth channel here too?
A fifth channel, and the hairs are reading it. Rapid variations in a were related to whether a bloom held a , and flies that met those variations were more likely to return to that flower. turned out to govern the polarity of the charge a fly carries, the same arrangement bumblebees use. Recordings from the antennae showed no sensitivity to the field at all.
A flower signals on several channels at once. Color, shape and scent are the obvious ones, and warmth is a quieter fourth that some pollinators use. Bumblebees added a fifth some years ago, when they turned out to sense the electric field surrounding a bloom.
Hoverflies are among the most important dipteran pollinators, and nobody had asked whether they do the same. Khan and colleagues took Eristalis tenax and Cheilosia albipila and worked through the electrical side of the interaction. How does a fly acquire a charge in the first place, and what is the field around a target flower doing?
Rapid variations in the floral electric field were related to whether the flower held a nectar reward, and flies that encountered those variations were more likely to visit again. That is the part with value for the insect. An electrical signal that tracks the state of the stock beats one that only names the shop.
Where the sensing happens is the other half of the work. Thoracic hairs played a role in setting the polarity of a hoverfly’s charge, which reveals an electro-mechanosensory capability like the one in Bombus terrestris. Electrophysiological recordings from the antennae showed no neural sensitivity to the field, which leaves the mechanosensory hairs as the likely receptive organs in both species.
wat. The flower advertises its stock electrically, and the fly reads the notice with the hairs on its chest.
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Electrical signalling was looking like a bee speciality. Finding it in flies widens it to a different order of insects and a very different body.
How do we know?
Khan and colleagues measured how hoverflies acquire charge, how the electric field around a flower varies with its nectar, and whether the antennae respond electrically to such a field.
What is still unknown
Two hoverfly species under controlled conditions, and the role of the hairs rests on an absence of response in the antennae rather than on a recording from a hair itself.
Learn something?
Where to next
Why would an electric eel climb out of the water to attack?electricity
When does a pollinated flower stop advertising?flowers
What breaks first when flowers and their bees get a warmer spring?flowers