Chromatic, achromatic and bimodal negative patterning discrimination by free-flying bumble bees

Negative patterning discrimination is considered a nonelemental form of learning, and has been extensively investigated across taxa. Several insect species have also been examined with this task, but only honey bees, Apis mellifera, have so far demonstrated this capacity. Recent empirical and theoretical studies suggest that negative patterning can be accounted for by the emergent property of the mushroom body circuitry in the honey bee brain. Given the neurobiological similarity between bumble bees and honey bees, we hypothesized that bumble bees should also have this cognitive capacity. Here we showed that free-flying bumble bees, Bombus terrestris, learned chromatic, achromatic and visual-olfactory bimodal negative patterning discrimination. Further analyses showed that individual bumble bees adopted distinct strategies in approaching negative patterning discrimination, some solving the task in a configural manner, while others solved it via a simpler strategy. Our findings are in contrast to previous work using harnessed bumble bees and highlight the importance of designing experiments around the requirements of specific species. Our results add to our knowledge on insect nonelemental learning and open up new opportunities for examining cognitive limitations and individual decision-making strategies.