Many insects have close associations with microbes, though the nature of the relationship is often unknown. In one such case, facultative bacteria have been discovered in the hindgut of a major crop pest and virus vector, the Western flower thrips (WFT), Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae). These bacteria can be cultured outside thrips and are horizontally transmitted among WFT. Several thrips bacterial isolates have been studied in the Netherlands. Molecular data indicated WFT symbionts were monophyletic and similar to Escherichia coli, though biochemical properties suggested these microbes might actually be most similar to plant pathogens in Erwinia. We focused on the bacterial flora of WFT originating from the Hawaiian Islands. Molecular phylogenetic analyses based on the 16S rDNA gene showed that bacteria from thrips originating in the Hawaiian Islands and Netherlands were very similar. Phylogenetic data also suggested two polyphyletic groups of WFT bacteria were present in isolates from both geographic regions. One of the groups fell out closely with Erwinia; however, bootstrap values for this classification were low. The second group did not cluster with any one group of bacteria. Further examinations of thrips collected from various locations in the Western United States show thrips bacteria are widespread in WFT populations.