This mite was described by Froggatt as attacking oats in New South Wales in 1921 (Agric. Gaz. N.S.W. 3rd Jan. 1921) under the name of Notophallus bicolor, sp. n., but with a very inadequate description. In my paper of 1933 “ On some Acarina from Australia and South Africa ” (Trans. Roy. Soc. South Aust. 57, pp. 108–112) I recorded it from the Cape Town area of South Africa, as well as from certain States of the Australian Commonwealth, giving a redescription and detailed figures. The generic name was changed to Penthaleus, as it had been shown that Notophallus of Canestrini 1886 was synonymous with Koch's Penthaleus of 1838. At that time, although so far as I was aware no recent redescription of any of the European species of Penthaleus had been published, I gave P. bicolor (Frog.) as doubtfully synonymous with P. major (Dugès 1834), a species considered by European workers as the same as P. haematopus, Koch 1835, and P. insulanus, Thorell, 1872.