Age-related differences in learning, memory and brain plasticity in workers of the common wasp, Vespula vulgaris.

Learning, memory and brain plasticity are thought to play an important role in regulating behavioural roles in social insects, as workers perform different tasks as nurses, builders, foragers and defenders. However, it remains challenging to disentangle whether neural changes regulate behaviour or arise as a consequence of it. While cognition has been extensively studied, especially in honeybees, the variation of cognitive traits remains poorly understood in social wasps. Here, we investigated age-related changes in learning, memory and neuroanatomy in workers of the common wasp, Vespula vulgaris. We developed a Y-maze to test differential conditioning and memory of wasps and later visualised the brains using a high-resolution micro-computed tomography imaging. We found that younger individuals exhibited slower decision making yet made more accurate decisions compared with older individuals, revealing a pronounced speed-accuracy trade-off. Short-term memory showed only a slight decline with age. Neuroanatomical image analysis revealed that, despite a reduction in overall brain volume, key major neuropils involved in sensory processing and learning, such as mushroom bodies, optic lobes and antennal lobes, increased in relative volume with age. These findings corroborate with studies in bees and provide novel insights into how ageing influences cognitive function and brain structure in wasps.