In the 1980?s Haplaxius (Myndus) crudus (Cixiidae) was reported to be the vector of the phytoplasma disease "lethal yellowing" (LY) of coconut palm in Florida. Most recently, the LY phytoplasmas have been shown to belong to the group 16S rIV-A. Transmission of the 16Sr IV-D phytoplasma ("Texas Phoenix palm decline") by H. crudus to Pritchardia pacifica was obtained in Yucatan, however transmission to coconut was not demonstrable. The taxonomy of the Cixiidae is confounding owing to the often cryptic nature of closely related variants and species, particularly of the tribe Oeclini Muir, 1922 to which Haplaxius belongs. Recently several Myndus species were transferred to other genera. Haplaxius itself was moved to the genus Myndus and re-classified as Haplaxius. In 2008 it was shown that phylogenetic trees reconstructed using the cytochrome oxidase I gene (mtCOI) and the 18S rDNA sequences were congruent, and that the trees were consistent with morphological classification for Oeclini. The highly evolving mitochondrial mtCOI were used to ascertain if differences occurred between H. crudus populations from Mexico with respect to the transmission of group 16S rIV-A and 16S rIV-D. Results indicated that two haplotypes of H. crudus exist in Mexico, possibly involved in the transmission of one of the two phytoplasma groups.