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 seldomly been tested experimentally under field conditions. Here, I studied the anti-predatory functions of the decoration (bag) of a bagworm moth, Eumeta crameri against their natural predator, Oecophylla smaragdina, the Asian weaver ant. I experimentally tested if bag removal from caterpillars resulted in more predation than bagged caterpillar under field conditions, which would support the hypothesis that bags are selected to protect the caterpillars against their predators. In support of that, I showed that caterpillars without a bag were attacked, killed and taken to ants nest significantly more than bagged caterpillars. My study provides rare experimental evidence for anti-predatory functions of the decoration. My study suggests that decorating behaviour has evolved in animals as an anti-predatory defence mechanism.