The following five new species of Atrichopogon Kieffer from southern Argentina and Chile are described and illustrated: A. aridus Spinelli & Marino, A. comechingon S. & M., A. endemicus S. & M., A. inacayali S. & M. and A. similis S. & M. A. aridus and A. comechingon also occur north of Patagonia. The previously known species A. obfuscatus Ingram & Macfie is redescribed, and notes on its type are provided. A key to recognition of males and females of the seven species inhabiting Patagonia is included. A biogeographic parsimony analysis of endemicity (PAE) interprets the relationships among the provinces of the southern South America. It is based on seven areas of endemism and distributional data of 30 species of the subfamily Forcipomyiinae. The analysis results in two most parsimonious cladograms and their strict consensus depicts the following relationships: ((Monte, Patagonian steppe) (Central Chile, Magellanic Moorland (Magellanic Forest, Maule, Valdivian Forest))).