Do wild-caught fly larvae cooperatively forage?

Animals often form organized cooperative foraging groups, where individual members must adhere to specific rules to maintain cohesiveness. These groups face the challenge of managing potential intruders, who may or may not assist in foraging. In semi-liquid food environments, Drosophila larvae learn to synchronize their movements into clusters, which are thought to make feeding more efficient. Individuals who do not synchronize with the group are excluded from the cluster. Whether clustering behavior occurs in wild-caught larvae, and if so, the extent of their selectivity in group membership, remains unknown. Here, we show that clustering occurs across a number of fly species, and the capacity to join different clusters varies both between and within species. We collected and observed a larval cluster from rotting fruit in the field, yielding seven fly species. Subsequent tests for clustering on five lines from this collection and 20 other inbred wild-caught lines revealed that all species, except D. suzukii, exhibit clustering behavior. Each line demonstrates varying capacities to become members of different clusters. This study also indicates that there is high genetic variance in how individual lines cluster with each other that is not explained by cross species features. Additionally, combinations of wild species with lab benchmark strains give varied outcomes in resultant adult fitness. The ability to co-cluster varies between and within species boundaries. However, fly lines that cluster with another tend to impart fitness both to themselves and their host. Our findings demonstrate that multiple species of fly larvae can co-cluster. This behavior tends to confer mutual benefits to cluster members, suggesting significant ecological implications in Drosophila communities.