Phenology of Kleptobiotic Sundew Bugs Tracks Peak Stickiness of Their Carnivorous Host Plants

Drosera L. (Droseraceae) is a diverse genus of carnivorous plants that is cosmopolitan in distribution, with Australia its centre of diversity (ca. 160 species in Australia). Collectively known as sundews, their leaves are covered with mobile sticky hairs (“tentacles”) that serve as active flypaper‐type traps that catch small invertebrates. This prey is then digested with enzymes and absorbed as nutrition for the plant. Not all invertebrates fall prey to sundews, with sundew bug species of the genus Setocoris China & Carvalho, 1951 (Miridae) avoiding capture and stealing the plant's prey, in an unusual case of kleptobiosis. This specialised interaction suggests that the bug and host plant are highly co‐adapted, although most aspects of the natural history of this interaction are poorly understood. In this study, field observations made over the course of 3 months show that the undescribed species Setocoris n.sp_BINA are first present on their host plants ( Drosera binata Labill. and Drosera peltata Thunb.) when plants are sticky and catching prey. Sundew bugs are observed first on D. peltata and then D. binata , corresponding to the differing phenologies of each host plant species. These observations generated the following hypotheses for future testing: (1) S. n.sp_BINA move between host species to prioritise prey availability, and (2) S. n.sp_BINA eclosion is triggered by the same moisture and/or temperature cues as their hosts so that hatching coincides with prey availability.