Molecular analyses indicate that Turlock virus (TUR, Turlock serogroup) and Boraceia virus (BOR, Anopheles B serogroup) have virion RNA species and polypeptides comparable in size to those of members of the Bunyavirus genus and unlike those of members of the newly defined Phlebovirus, Nairovirus, or Uukuvirus genera (Bunyaviridae). The 11 terminal 3′ end nucleotides of the three virion RNA species of both BOR and TUR viruses (HOUCAUCACAUG …) are identical in sequence to the 3′ end sequences of the viral RNA species of snowshoe hare (SSH) and La Crosse bunyaviruses (LAC, California serogroup, Bunyavirus genus). Competition radioimmune assays (RIA), using iodinated LAC nucleocapsid polypeptide (N), or LAC glycoproteins (G1, G2), and LAC rabbit hyperimmune anti-sera, or iodinated Oriboca (ORI, Group C, Bunyavirus genus) N, or G1 and G2 polypeptides and LAC antisera, or iodinated Bunyamwera (BUN, Bunyamwera serogroup, Bunyavirus genus) N, or G1 and G2 polypeptides and BUN or LAC antisera, have indicated that the virion polypeptides of BOR virus share antigenic determinants with these other bunyaviruses. Competition RIA analyses also have shown that TUR virus shares antigenic determinants with LAC virus. The competition RIA analyses have confirmed the antigenic relationships of LAC, SSH, trivittatus, Bwamba, Aino, Simbu, Mermet, Guaroa, Lumbo, Tahyna, ORI, Anopheles A, BUN, Capim, Guama and Shark river viruses (Bunyavirus genus members), and lack of antigenic relationships between Karimabad, or Chagres, or sandfly fever, Sicilian, viruses (Phlebovirus genus members), and the bunyaviruses, LAC, ORI, or BUN.