Abstract
Chromosome systems of 12 genera and 36 species of the North American Decticinae have been studied. The chromosome number of these species ranges from 2n=22 to 2n=31 in the male (see Table 2). Robertsonian changes has played an important role in chromosome evolution in these decticines. Neduba sp. has a neo-XY sex determining mechanism and Neduba diminutiva an X1X2Y one.
The probable pathways of chromosome evolution and the origin of the neo-XY and -X1X2Y sex determining mechanisms are discussed, as well as the phylogeny and present taxonomic status of the North American Decticinae based on chromosome systems.
