Flexible visual learning in nectar-foraging hornets

Abstract

Abstract Pollinators, such as bees, develop flexible memories of colors, patterns, and shapes, for efficient flower recognition. Here we tested whether other flower-foraging insects have evolved similar cognitive abilities underpinning flexible visual learning. We trained wild hornets from two species commonly found in Europe, the invasive yellow-legged hornet (Vespa velutina nigrithorax) and the European hornet (Vespa crabro), to associate sucrose solution rewards to color stimuli in a Y-maze. Hornets from both species succeeded in differential and reversal learning and developed short-term memories of the learnt associations. Thus, just like bees, hornets can learn various visual cue-reward associations and remember them for at least 1 h for selecting flowers. Our study in non-model species illustrates how standard conditioning approaches can be used to explore and compare the cognitive abilities of animals sharing similar foraging ecologies. Significance statement Bees can learn an impressive diversity of visual cues to recognize the best rewarding flowers. This can be studied using Y-maze in which individual insects must learn to associate visual stimuli to the presence or absence of nectar rewards. Here, using the same approach, we show that hornets are also capable of these associations. We compared the learning abilities of hornets from two common species in Europe and found that they could similarly learn to discriminate two colors and keep this information in memory for at least 1 h. Hornets thus evolved visual cognition facilitating robust flower foraging, like bees and many other pollinators.