Dear Editor,
Two species of imported fire ants,the red imported fire ant,Solenopsis invicta Buren,and the black imported fire ant,Solenopsis richteri Forel,were introduced into the United States from South America at the port of Mobile,Alabama in 1918 and 1930s,respectively.Although S.richteri was introduced and established in the United States more than one decade earlier than S.invicta,the latter has gradually displaced S.richteri throughout most of its distribution.However,S.richteri still persist in areas along the northern boundary ofS.invicta's distribution range,including northern Alabama,north Mississippi and southern Tennessee (Streett et al.,2006;Tschinkel,2006;Oliver et al.,2009).Hybridization occurs between these 2 species in the United States (Vander Meer et al.,1985).