Group living is ubiquitous in nature, and social foraging is among the common forms of cooperative behaviour in animals. Understanding the evolution and maintenance of social foraging requires knowledge of the underlying benefits and costs to group members, though these are only known for few model taxa, which often lie at the extremes of social organisation. Here, we experimentally examined hypothesised benefits and costs of social foraging in the velvet worm Euperipatoides rowelli; the only Onychophoran currently known to live and forage in groups. To explore benefits, we tested the effects of natural group size and controlled prey size on the latency to attack and begin consuming prey, the likelihood of complete prey consumption and the time taken to completely consume prey. Our focal cost was aggressive intraspecific interactions in the form of biting, kicking and striking, which may present a particular risk to soft-bodied velvet worms. As predicted, we found a positive scaling of