Abstract
Four new species of Simulium (subgenus Morops Enderlein) are described. S. dycei sp. n. and S. mackerrasorum sp. n. are both widespread and abundant in north Queensland and the Northern Territory, with S. mackerrasorum extending into Western Australia. S. standfasti sp. n. from Carnarvon Gorge, Queensland, and S. lawnhillense sp. n. from near Lawn Hill, north Queensland, and Arnhem Land, Northern Territory, appear to have a very restricted distribution. A key to all Australian species of Simulium is given, as well as maps of their distribution and a brief comment on the distribution of Simulium in Australia.