A device (1) for trapping animal pests such as caterpillars, having a collar (2) which is designed to surround the trunk of a tree (3), the collar (2) including a substantially annular walkway (4) that extends substantially in a first plane (P1) that is intended to be oriented horizontally. Joining means (31) including an arrangement (32) of flexible bristles (33) having a suitable density prevent the animal pests from passing between the collar (2) and the trunk of the tree (3).