GEOGRAPHIC-DISTRIBUTION AND BIOGEOGRAPHY OF REPRESENTATIVE SPECIES OFXERIC GRASSLAND-ADAPTED NEARCTIC LYGAEIDAE IN WESTERN NORTH-AMERICA (INSECTA, HETEROPTERA)

This paper outlines the known distribution of eight xeric grassland-ad apted species of Lygaeidae, and examines these distributions with resp ect to the glacial history of North America during the Pleistocene, an d past and present distribution of grassland vegetation. Four of these species (Neosuris castanea, Sisamnes claviger, Ligyrocoris latimargin atus, and Melanopleurus perplexus) probably survived the Pleistocene i n refugia south of the Late Wisconsinan ice sheet. Differences in clim atic requirements may explain the variations in geographic distributio n exhibited by these four insects and a methodology for testing this i s discussed. The four other species (Crophius ramosus, Kolenetrus plen us, Slaterobius insignis, and Emblethis vicarius) may have occurred in the north prior to 1.2 mya and survived the Late Pleistocene in both the northern Beringian refugium and in southern refugia. Molecular sys tematics, especially use of DNA restriction site or sequence data, mig ht provide the evidence needed to test historical biogeographic postul ates based on the extant distribution of these species.