Journal of Vector Ecology 347 Vol. 30, no. 2 Keyword index: Ochlerotatus japonicus, Missouri, exotic species, invasive species. Scientific Note First occurrence of Ochlerotatus japonicus in Missouri Stephanie Gallitano 1, , Leon Blaustein 1,2,3 , and James Vonesh 1 1 Tyson Research Center, Biology Department, Washington University in St. Louis, Eureka MO 63025 U.S.A. 2 Mosquito Research Labs, Entomology Department, Rutgers University, 180 Jones Avenue, New Brunswick NJ 08901 U.S.A. 3 Community Ecology Laboratory, Institute of Evolution, Faculty of Sciences, University of Haifa, Haifa 31905 Israel Received 15 August 2006; Accepted 26 August 2006 The container-breeding mosquito, Ochlerotatus japonicus japonicus (Theobold), is native to Japan and the eastern coast of Asia (Tanaka et al. 1979). In 1998, this species was first reported in the United States, in Ocean County, New Jersey and Suffolk County, New York (Crans 1999, Peyton et al. 1999, Romanowski et al. 1999, Scott et al. 1999). By 2003, it had been reported in at least 19 other states in the eastern US as well as to Quebec, Canada (http://www.rci.rutgers.edu/ ~insects/ocjap.htm), and in 2004 it was reported from western Washington (Roppo et al. 2004). The expansion of this exotic species in North America has been watched with concern as it has been shown to be a potential vector of St. Louis Encephalitis and West Nile virus (Sardelis and Turell 2001, 2003). On June 14, 2005, we collected and identified Oc. j. japonicus larvae from artificial containers at Washington University’s Tyson Research Center in western St. Louis County (Geographic: 38°-31’ 33.6399”\90°-33’ 36.9512”; UTM: 980372.24’\802968.29’). Tyson is characterized by a hilly, karst-dominated landscape about 85% of which is covered in oak-hickory forest. This represents the first record of this species in the state of Missouri. To further evaluate the establishment of Oc. japonicus, on July 22, we haphazardly collected 10 mosquito larvae from 15 artificial pools widely spread throughout Tyson Research Center. These pools were initially established on June 23 with 300L of dechlorinated water, oak and hickory leaf litter, and an inoculation of zoo/phytoplankton as part of an experiment assessing treefrog oviposition site selection. A survey of natural container habitats was not possible during this period due to a drought. Immature Oc. japonicus were found in the samples in nine of the 15 pools along with several other species, population composition recorded in Table 1. These data suggest that Oc. japonicus is established at Tyson Research Center being the second most common mosquito species overall. This represents the western most record of this exotic species in the central and eastern United States. The nearest previous records place Oc. Japonicus in Michigan (2003, Tom Wilmot pers com) to the east and Washington (Roppo et al.) state to the west of Missouri. Given the likelihood that the occurrence of this species is from a spread from the east, our record suggests the possible presence of this exotic in the nearby states, such as Illinois. More widespread surveys of Oc. japonicus should be taken throughout the Missouri and other midwestern and prairie states in order to determine the extent of Oc. japonicus in this region. Acknowledgments We thank Wayne Crans for confirming our identifications. We would also like to thank Richard Lampman, Linn Haramis, Uriel Kitron, Steve Juliano, Jack Swanson, and Tom Wilmot for their correspondence concerning expansion of Oc. japonicus. REFERENCES CITED Crans, W. J. 1999. Aedes japonicus: accidental introduction to the northeastern United States. Vector Ecol. Newsl. 30: 5. Peyton, E. L., S. R. Campbell, T. M. Candeletti, M. Romanowski, and W. J. Crans. 1999. Aedes (Finlaya)japonicus japonicus (Theobald), a new introduction into the United States. J. Am. Mosq. Contr. Assoc. 15: 238-241. Romanowski, M., T. Candeletti, S. Campbell, D. Ninivaggi, and W. J. Crans. 1999. Aedes japonicus in New Jersey and New York- the first United States records. In: Hamilton G.C., ed. Proceedings of the 86 th meeting of Species Number of pools containing species Percent of total larvae collected Cx. pipiens 11 0.31 Cx. restuans 9 0.16 Cx. salinarius 8 0.17 Oc. japonicus 9 0.24 Aedes sp. 7 0.12 Table 1. Population composition of immature mosquitoes collected from 15 artificial pools at Tyson Research Center.