The first marsupial demodicid, Demodex antechini, is described with notes on its life cycle, sexual dimorphism and pathology. This species is remarkably similar except for the marked sexual dimorphism, to demodicids of eutherian mammals. This suggests an early origin and a long evolutionary history of parallelism within the genus.
Our thanks to Patricia Woolley, Waite Agricultural Institute, Glen Osmond, Australia, for the specimens used in preparing this paper. We would also like to thank Clifford Desch for the photography and the drawings. The work reported here was supported in part by NSF Grant (GB-3516).