The ecology, life history and morphometrics of the common chigger mite Eutrombicula samboni (Womersley, 1939) (Acarina: Trombiculidae) of south-eastern South Australia have been studied. Larvae were captured free-living, as well as ectoparasitic on Rattus fuscipes greyii. Captured ectoparasitic larvae have been reared to protonymphs and deutonymphs, which are described. Deutonymphs and adults caught in the field are compared with each other and the reared deutonymphs. Evidence is presented of a subadult stage being present, as occurs in the Microtrombidiidae. Morphometric data are presented of larvae, with the type series being compared with those collected near Robe, South Australia, as well as with the morphometric data of Womersley and Heaslip (1943) and Womersley (1952). The earlier measurements of Womersley & Heaslip were significantly (and less accurately) re-estimated in Womersley (1952). A brief historical review is given of trombiculid studies in the south-east of South Australia, with particular reference to the work of R. N. McCulloch.