The Vespidae is a diverse family of wasps and hornets that are formidable predators of insects, including social bees¹, and includes a number of invasive species². Recently, the world's largest hornet, Vespa mandarinia Smith (Hymenoptera: Vespidae), which occurs naturally in the Indomalayan region, has been found in Canada and the United States². Some simulations indicate that it could rapidly spread throughout Washington and Oregon in the western US, as well as some eastern parts of the country^2,3, threaten native bees and honeybees, and harm bee-pollinated crop production worth over $100 million annually³. There is consequently an urgent need to learn more about V. mandarinia's reproductive biology and to develop trapping methods to locate its nests and to control its reproduction. We identified V. mandarinia queen-produced sex pheromone from the 5^th and 6^th intersegmental sternal glands of virgin queens. The major active compounds were hexanoic acid, octanoic acid, and decanoic acid. When placed in field traps, the synthetic compounds and a queen-equivalent mixture rapidly attracted hundreds of males but no females or other species.

Honey bees use a complex form of spatial referential communication. Their "waggle dance" communicates the direction, distance, and quality of a resource to nestmates by encoding celestial cues, retinal optic flow, and relative food value into motion and sound within the nest. We show that correct waggle dancing requires social learning. Bees without the opportunity to follow any dances before they first danced produced significantly more disordered dances with larger waggle angle divergence errors and encoded distance incorrectly. The former deficit improved with experience, but distance encoding was set for life. The first dances of bees that could follow other dancers showed neither impairment. Social learning, therefore, shapes honey bee signaling, as it does communication in human infants, birds, and multiple other vertebrate species.

Honey bees use a complex form of spatial referential communication. Their waggle dance communicates to nestmates the direction, distance, and quality of a resource by encoding celestial cues, retinal optic flow, and relative food value into motion and sound within the nest. This protocol was developed to investigate the potential for social learning of this waggle dance. Using this protocol, we showed that correct waggle dancing requires social learning. Bees (Apis mellifera) that did not follow any dances before they first danced produced significantly more disordered dances, with larger waggle angle divergence errors, and encoded distance incorrectly. The former deficits improved with experience, but distance encoding was set for life. The first dances of bees that could follow other dancers had none of these impairments. Social learning, therefore, shapes honey bee signaling, as it does communication in human infants, birds, and multiple other vertebrate species. However, much remains to be learned about insects' social learning, and this protocol will help to address knowledge gaps in the understanding of sophisticated social signal learning, particularly in understanding the molecular bases for such learning. Key features It was unclear if honey bees (Apis mellifera) could improve their waggle dance by following experienced dancers before they first waggle dance. Honey bees perform their first waggle dances with more errors if they cannot follow experienced waggle dancers first. Directional and disorder errors improved over time, but distance error was maintained. Bees in experimental colonies continued to communicate longer distances than control bees. Dancing correctly, with less directional error and disorder, requires social learning. Distance encoding in the honey bee dance is largely genetic but may also include a component of cultural transmission.

The co-evolutionary arms race between predators and their prey has led to complex signalling, especially in groups that benefit from the social transmission of alarm signals. In particular, pursuit deterrence signals can allow individuals and groups to indicate, at relatively low cost, that a predator's further approach is futile. Pursuit deterrence signals are usually more effective if amplified, for example, by becoming contagious and rapidly spreading among prey without requiring individual prey to confirm predator presence. However, this can also lead to runaway false signalling. We provide the first evidence of a contagious pursuit deterrence signal in social insects. The Asian honey bee Apis cerana, performs an I See You (ISY) signal that deters attacking hornets. We show that these signals enhance defensive signalling by also attracting guard bees and that the visual movements of appropriate stimuli alone (hornets and ISY signalling bees, but not harmless butterflies) provide sufficient stimuli. Olfaction and other potential cues are not necessary. The ISY signal is visually contagious and is buffered from runaway false signals because it is specifically triggered and by likely selection for honesty within the highly cooperative bee colony. These results expand our understanding of contagious signals and how they can be honestly maintained in highly cooperative collectives.

The heat ball defense of honey bees against their sympatric hornet predators is a classic and spectacular outcome of a co-evolutionary race. Hundreds of bees can encapsulate a hornet within a large ball that kills it with elevated heat. However, the role of stinging in this defense has been discounted, even though sting venom is an important weapon in bees. Surprisingly, no studies have tested the role of bee sting venom alone or in conjunction with elevated temperature on hornet survival. We surveyed dead Vespa velutina hornets found near and inside Apis cerana colonies and found stings retained in hornet bodies, most often in an intersegmental neck-like region, the veracervix. Experimentally stinging hornets in this region with A. cerana and Apis mellifera guards significantly increased hornet mortality. The combination of sting venom and elevated heat ball temperature (44 °C) was the most lethal, although there was no synergistic interaction between sting venom and temperature. As expected, hornet mortality increased when they were stung more often. The average amount of venom per insect species and the length of stinger lancets correlated with insect mass. Sting venom thus remains important in the arms race between bees and their hornet predators.

Concern is growing over the effects of neonicotinoid pesticides, which can impair honey bee cognition. We provide the first demonstration that sublethal concentrations of imidacloprid can harm honey bee decision-making about danger by significantly increasing the probability of a bee visiting a dangerous food source. Apis cerana is a native bee that is an important pollinator of agricultural crops and native plants in Asia. When foraging on nectar containing 40 µg/L (34 ppb) imidacloprid, honey bees (Apis cerana) showed no aversion to a feeder with a hornet predator, and 1.8 fold more bees chose the dangerous feeder as compared to control bees. Control bees exhibited significant predator avoidance. We also give the first evidence that foraging by A. cerana workers can be inhibited by sublethal concentrations of the pesticide, imidacloprid, which is widely used in Asia. Compared to bees collecting uncontaminated nectar, 23% fewer foragers returned to collect the nectar with 40 µg/L imidacloprid. Bees that did return respectively collected 46% and 63% less nectar containing 20 µg/L and 40 µg/L imidacloprid. These results suggest that the effects of neonicotinoids on honey bee decision-making and other advanced cognitive functions should be explored. Moreover, research should extend beyond the classic model, the European honey bee (A. mellifera), to other important bee species.

This corrects the article DOI: 10.1038/srep44640.

Animal-pollinated plants face a common problem, how their defensive anti-herbivore compounds may impair or alter pollinator behavior. Evolution has tailored multiple solutions, which largely involve pollinator tolerance or manipulation, to the benefit of the plant, not the removal of these compounds from pollen or nectar. The tea plant, Camilla sinensis, is famous for the caffeine and tea polyphenols (TP) that it produces in its leaves. However, these compounds are also found in its nectar, which honey bees readily collect. We examined the effects of these compounds on bee foraging choices, learning, memory, and olfactory sensitivity. Foragers preferred a sucrose feeder with 100 µg or 10 µg TP/ml over a control feeder. Caffeine, but not TP, weakly increased honey bee learning. Both caffeine and TP significantly increased memory retention, even when tested 7 d after the last learning trial. In addition, TP generally elevated EAG responsiveness to alarm pheromone odors. These results demonstrate that other secondary plant compounds, not only caffeine, can attract pollinators and influence their learning and memory.