Using three-dimensional printed models to test for aposematism in a carabid beetle

Many studies have demonstrated that bright colours sometimes evolve as warning coloration on the bodies of distasteful prey. However, few studies have demonstrated that the bright structural colours of beetles function as such aposematic signals for predators in the wild. To determine whether body colour might act as an aposematic signal in the carabid beetle Damaster blaptoides, we generated beetle models and conducted camera-trap and field experiments. Elaborate beetle models produced using a three-dimensional printer were used to determine which animals attack them in the wild. Red and black models were placed in forests to test which of the two types was attacked the least frequently. The camera-trap experiments indicated that mammals and birds were the potential predators of D. blaptoides. The field experiments revealed that predators attacked the red models significantly less frequently than the black models in each of three sites where red Damaster subspecies were distributed. In three sites where black Damaster subspecies were distributed, predators attacked both red and black models at similar rates. These results might imply that the predators learned more easily to avoid distasteful red beetles rather than black ones.