PCR amplification of the Ace . 2 gene. Larvae collected at various cemeteries in Mexico City were reared to mosquito adults and then identified by PCR amplification of the Ace.2 gene . The Cx. p. pipiens specific band of 610 bp and Cx. p. quinquefasciatus specific band of 274 bp and the expected bands of 610 and 274 bp for hybrids (panel B) are displayed in the agarose gels. *Cx. tarsalis identified by morphological analysis did not produce a PCR amplicon. †Culex spp. mosquitoes that were not identified as pertaining to the Cx. pipiens complex or hybrids by morphological analysis or by the Ace.2 gene assay.