Fig. 7. Regional homologies among diverse arthropod body plans. The proposed relationships between insects, myriapods, anostracans and malacostracan crustaceans are based on patterns of Hox gene expression, indicated by colours: Antp, Ubx and AbdA in yellow; AbdB in red; Cad in purple (Averof and Akam, 1995; Abzhanov and Kaufman, 2000a; Abzhanov and Kaufman, 2000b; Hughes and Kaufman, 2002c). The post-genital region appears to be a unique region arising between the AbdB- and Cad-expressing domains in anostracan crustaceans, with no obvious counterpart in insects, myriapods and malacostracan crustaceans. The proposed relationships with body regions of cephalocarids and copepods are hypothetical (broken lines), based on similarities in the overall patterns of tagmosis and segmental specialisation among these groups (Averof and Akam, 1995; Walossek and Muller, 1997).