Honey Bees Modulate Their Olfactory Learning in the Presence of Hornet Predators and Alarm Component

Abstract

In Southeast Asia the native honey bee species Apis cerana is often attacked by hornets (Vespa velutina), mainly in the period from April to November. During the co-evolution of these two species honey bees have developed several strategies to defend themselves such as learning the odors of hornets and releasing alarm components to inform other mates. However, so far little is known about whether and how honey bees modulate their olfactory learning in the presence of the hornet predator and alarm components of honey bee itself. In the present study, we test for associative olfactory learning of A. cerana in the presence of predator odors, the alarm pheromone component isopentyl acetate (IPA), or a floral odor (hexanal) as a control. The results show that bees can detect live hornet odors, that there is almost no association between the innately aversive hornet odor and the appetitive stimulus sucrose, and that IPA is less well associated with an appetitive stimulus when compared with a floral odor. In order to imitate natural conditions, e.g. when bees are foraging on flowers and a predator shows up, or alarm pheromone is released by a captured mate, we tested combinations of the hornet odor and floral odor, or IPA and floral odor. Both of these combinations led to reduced learning scores. This study aims to contribute to a better understanding of the prey-predator system between A. cerana and V. velutina.

Pheromones modulate reward responsiveness and non-associative learning in honey bees

“…Among them, IPA presence would be crucial to set the threshold level, lowering it and facilitating aggression. This model accounts for the facts that IPA impairs appetitive learning in bees 38 , 41 and that some appetitive floral odors attenuate IPA-induced aggression in bees 40 . Our finding that pheromones with positive and negative valence directly affect sucrose responsiveness in an opposite way suggests that pheromones directly modulate thresholds of responsiveness, ultimately affecting decision making in bees.…”

Vespa velutina: An Alien Driver of Honey Bee Colony Losses

“…collapse in late autumn or winter, while newly-mated queens search for a place where they can overwinter and, the following year, they start a new cycle [8,27,34,35], Figure 2. Hornets use olfactory stimuli to search for long-distance food sources, especially with regard to the localization of honey bee colonies, but the nature of these stimuli is not yet entirely clear [36][37][38].…”

“…The species can cause serious damage and imbalances to biodiversity and ecosystems in areas where it has been introduced. This is aided by V. v. nigrithorax's high reproductive rate, high Hornets use olfactory stimuli to search for long-distance food sources, especially with regard to the localization of honey bee colonies, but the nature of these stimuli is not yet entirely clear [36][37][38].…”

C-type allatostatins mimic stress-related effects of alarm pheromone on honey bee learning and memory recall

“…These responses include a slowing of the rate at which bees learn to associate odours with a food reward [6–9]. Parallels can be observed in rats, which show a lowering of appetitive-related behaviours in response to stress [10].…”