Chemotactile perception and associative learning of amino acids in yellowjacket workers.

Learning and memory are fundamental processes, influencing animal foraging behaviour and fitness success. Evaluating food nutritional quality, particularly of proteins and essential amino acids, involves complex sensory mechanisms. While olfactory cues have been extensively studied, less is known about proteinaceous chemoreception, especially in invertebrates. Vespula germanica, a globally invasive social wasp species, relies heavily on foraging efficiency and nutritional assessment for colony success. Previous studies have highlighted their associative learning abilities in natural settings, but their cognitive capabilities under laboratory conditions still need to be explored. We investigated the perceptual and learning abilities of V. germanica concerning amino acids using a maxilla-labium extension response (MaLER) conditioning protocol. We aimed to determine whether these wasps can (1) perceive specific amino acids through antennal chemoreception, (2) perform associative learning with amino acids, (3) discriminate between stimuli of varying molecular and nutritional profiles, and (4) generalize among similar stimuli. Our results suggest that V. germanica can detect free amino acids and exhibit associative learning toward them. They can discriminate between amino acids with different profiles and do not generalize among similar compounds. These findings indicate that V. germanica foragers can qualitatively evaluate amino acid solutions, which translates into a natural ability to discern and learn from food sources with varying nutritional qualities. This knowledge could enhance management strategies for this invasive species, which rely on poisoned beef-based baits. Understanding the sensory and cognitive capabilities of V. germanica provides a foundation for developing more effective control methods.