Feeding ecology of Australian Christmas beetles (Coleoptera: Scarabaeidae: Rutelinae): Implications for conservation and habitat management

Abstract

Christmas beetles (subfamily Rutelinae, genera Anoplognathus, Calloodes and Repsimus) are an ecologically important and culturally significant group of Australian scarabs, known for their striking appearance and seasonal mass emergences. Over the last decade, anecdotal reports suggest widespread population declines, raising concerns about their conservation status. Despite their prominence in Australian ecosystems, critical deficits remain in our understanding of their biology, particularly regarding their feeding ecology and larval habitat requirements. We reviewed available literature regarding adult and larval Christmas beetle feeding ecology, particularly feeding preferences, host plants and food finding behaviours. Our literature review found significant gaps in our knowledge of Christmas beetle feeding ecology: adult host plant association data were available for only 25 of the 44 described species of Christmas beetles. For larvae, our literature search identified feeding ecology information for only nine species. With the exception of a single study, all data regarding larval feeding came from observational studies rather than feeding trials. Notably, the only feeding trial we found failed to identify the larvae to species, significantly limiting the applicability of its findings. The limited information identified in this review highlights the urgent need for targeted research into the feeding ecology of Christmas beetles. The scarcity of data on larval feeding, in particular, limits our ability to determine how changes in land use, soil conditions, and plant communities impact their populations. Future studies incorporating feeding trials, long-term field observations, and experimental approaches will be critical for better understanding Christmas beetle ecology, especially for assessing their ecological roles, identifying key habitats, and developing effective conservation strategies where needed. Given the increasing concerns over Christmas beetle declines, prioritising research on their habitat requirements and resource use will help to ensure the conservation of these iconic Australian insects.