Asian hive bees have developed a synchronized ‘don’t-even-bother’ signal for would-be predators, according to a team of entomologists.
Apis cerana bees are quite capable of overcoming predatory hornets if they have adequate time to prepare. The bees will encase a hornet in a ball of hundreds of their own bodies, killing it with heat and suffocation (as shown in the video below).
To avoid actually having to go to this trouble, the bees have also perfected a massed warning display, report Benjamin Oldroyd, who studies behavioural genetics and social behaviour at the University of Sydney, and his colleagues. Guard bees at A. cerana hives will simultaneously vibrate their abdomens when a predator approaches, producing both a visual signal and a loud noise.
This, says the team, is the first example of an insect ‘I See You’ (ISY) display. These signals tell the predator not to bother attacking, saving the prey from having to defend against the attack and the predator from wasting its energy on a futile — and possibly dangerous — attempt.
To prove that this ‘simultaneous abdomen vibration’ was indeed an ISY display, the team placed free-flying predatory Vespa velutina hornets, tethered hornets and butterflies near Asian bee hives and another species of bee that evolved without hornet predation. If the researchers were correct, the Asian bee signal should have increased in intensity as the predators got closer, repelled the hornets and decreased predation relative to the other species. It should also have not been elicited by a non-threatening species.
All four predictions were borne out in the experiments.
“We do not wish to suggest that A. cerana uses its shaking display solely to repel V. velutina,” write the authors in Animal Behaviour. “The shaking display is used to deter non-hornet intruders, and is used in response to the presence of other species of hornet. However, we suggest that the intensity of the display, which is tuned to the movement and distance of a hornet, and the reduced response to a butterfly species that was both larger than a hornet and conspicuously coloured is evidence that the primary function of the display is to deter hornets.”
Image: wikipedia