Flowers use secret language to lure bees

Poppy
© University of Bristol | Floral heat patterns from poppies.

New research finds that beyond what humans can see and smell, flowers use hidden cues to attract their pollinators.

While we humans go about thinking we know everything that’s going on in the world … flowers and bees are busy all around us, communicating in ways that we don't have the capacity to sense. Researchers from the University of Bristol have discovered that many flowers produce not just signals that humans can see and smell, but also ones that are hidden to us, in this case, signals of heat.

The researchers used thermal imaging to study 118 species of flowers, of which 65 species (55 percent) – including many popular garden flowers – revealed complex patterns of heat in their petals. On average these patterns were 4 to 5 degrees Celsius warmer than the rest of the flower, although the patterns could be as much as 11 degrees Celsius warmer.

floral heat patterns© University of Bristol

The scientists conducted a number of experiments using artificial flowers that mimicked the heat patterns, but were plain in appearance. They looked alike to human eyes; but the bees could tell them apart. The heat patterns helped the bees select the “flowers” most likely to offer the most nectar.

The authors explain that bumblebees, honeybees and stingless bees use thermal detectors in their antennae and tarsi to help figure out which flowers are which.

“Bumblebees, who visit a wide range of different flowers, were found to be able to use these patterns to distinguish between different flowers and the rewards that they provide,” notes the University.

Dr. Heather Whitney, lead author of the study, says that "The presence of multiple cues on flowers is known to enhance the ability of bees to forage efficiently, so maximising the amount of food they can take back to sustain the rest of their colony.”

In addition to providing invisible messages to the bees, warm flowers offer another perq as well: they keep pollinators warm. Offering a cozy stop for insects while they do their work, the warmth allows the pollinators to maintain a body temperature above their minimum threshold for flying. “This allows pollinators to forage and collect nectar in colder conditions,” explain the authors, “and avoid the metabolic costs they might incur if they have to warm themselves for flight.”

Thus, heated petals and the patterns they offer serve as a boon to both bee and bloom … a secret language, of sorts; a beautiful little world, completely invisible to the human senses.

For more, you can read the study here: The diversity of floral temperature patterns, and their use by pollinators.

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