Boyeria irene larvae of different stages sampled at several localities in the headwaters of the Gardon River, Southern France, frequently showed malformations and injuries in their anal pyramid. The majority of these were broken or imperfectly regenerated tips of the anal spines. To quantify this phenomenon in a standardized way, exuviae of B. irene were sampled. In addition to running water habitats from the headwaters of the Gardon in France, exuviae from Lake Lucerne, Switzerland, were also analysed. In the Gardon river system, 9 to 26 % of the exuviae collected in 2008 showed damaged spines and para- or epiprocts. In Lake Lucerne, in 2006, 73 % of the exuviae were damaged. In most cases the tips of the epiproct or paraproct were broken or malformed. We interpret the damaged and malformed spiny appendages as indicating successful defence against fish attacks. When disturbed, anisopteran larvae spread out the elements of their anal pyramid presenting a spiky crown-like target. We hypothesise that this behaviour helps reduce the risk of being swallowed by predaceous fish. Presumably, most injuries are caused by the stresses the elements are subject to when puncturing the fish's mouth.