Bagworm decorations are an anti-predatory structure

Many animals decorate their exterior with environmental materials, and these decorations are predicted to increase their survival. The adaptive significance of these decorations, however, has seldom been tested experimentally under field conditions. This study researched the anti-predatory functions of the decoration (bag) of a bagworm moth, Eumeta crameri, against their natural predator, Oecophylla smaragdina, the Asian weaver ant. The study experimentally tested if bag removal from caterpillars resulted in more predation than bagged caterpillars under field conditions, which would support the hypothesis that bags are selected to protect the caterpillars against their predators. In support of the prediction, this study showed that caterpillars without a bag were attacked, killed, and taken to ants' nests significantly more than bagged caterpillars. The study provides rare experimental evidence for the anti-predatory functions of the decoration under field conditions. This study suggests that decorating behaviour has evolved in animals as an anti-predatory defence mechanism.