Better to risk limb than life: some insects use autotomy to escape passive predation by carnivorous plants

Abstract

Limb autotomy, the voluntary shedding of body parts as a strategy to escape predation or entrapment, is particularly common in insects and other arthropods that are frequently captured by the carnivorous plant genus Drosera. However, no study has previously examined the effectiveness of autotomy at facilitating escape from these passive, sessile plant predators. Using field observations of numerous Drosera species in Western Australia and Australia’s Northern Territory, we present the first field evidence of limb autotomy being employed by insects and other arthropods to escape capture by carnivorous plants. Most autotomised limbs found on the Drosera traps belonged to large nematoceran flies, probably comprised primarily of Tipulidae (crane flies), which have a characteristically large, slender body with very long limbs that seems likely to allow the effective use of autotomy as a strategy to prevent fatal capture. However, autotomy was overall only rarely observed amongst the Drosera prey as most prey items were small and quickly became completely enveloped by the sticky mucilage, rendering any such escape attempts impossible. Finally, we determined that the likelihood of escape decreased markedly as multiple limbs were lost.