A segment of the nuclear 28S rRNA gene was compared among six species of Lygus [Lygus hesperus (Knight), Lygus keltoni (Schwartz), Lygus borealis (Kelton), Lygus elisus (Van Duzee), Lygus lineolaris (Palisot de Beauvois), and Lygus vanduzeei (Knight)]. The DNA sequences were separate into three main groups. The LL group contains L. lineolaris and L. vanduzeei. Group LBLE is composed of L. elisus and most of L. borealis. Group LH includes L. hesperus and most of L. keltoni. Some L. keltoni were part of the LBLE group and some L. borealis were part of the LH group. The 28S region does not contain sufficient genetic polymorphism to delineate species. The apparent polyphyly of L. borealis and L. keltoni could reflect historic interbreeding, recent development of a hybrid swarm, or highlight inadequacies of morphospecies identification.