PROC. ENTOMOL. SOC. WASH. 109(1), 2007, pp. 240-248 FIRST REPORTED OCCURRENCE OF XYLEBORINUS ALNI (COLEOPTERA: CURCULIONIDAE: SCOLYTINAE) IN THE EASTERN UNITED STATES, WITH NOTES ON ITS RECOGNITION AND TREE HOSTS E. Richard Hoebeke and Robert J. Rabaglia (ERH) Department of Entomology, Comstock Hall, Cornell University, Ithaca, NY 14853-2601, U.S.A. (e-mail: [email protected]); (RJR) USDA Forest Service, Forest Health Protection, Arlington, VA 22209 (e-mail: [email protected]) Abstract. — Xylehorinus alni (Niisima), an Asian ambrosia beetle first detected in North America in the Pacific Northwest in the late 1990s, is reported for the first time from the eastern United States. Locality data for specimens captured in Lindgren funnel traps from nine eastern states are listed and mapped; these data suggest that this immigrant xyleborine is widely established in the Northeast. A habitus illustration and a diagnosis are provided to differentiate it from the other widespread immigrant Xyleborinus species in North America, X. saxesenii (Ratze-burg). Key Words: Coleoptera, Curculionidae, Scolytinae, Xyleborina, eastern United States, exotic species, new distribution records The genus Xyleborinus Reitter, pre-viously recognized by most authors either as a subgenus or a synonym of Xyleborus Eichhoff (Wood 1982), is comprised of at least 81 nominate species distributed worldwide (http://xyleborini. tamu.edu/browse.php?genus= Xyleborinus), with the majority occurring in Africa and Asia. Three species of the genus are found in America north of Mexico, two of which are endemic to Europe and Asia (Rabaglia et al. 2006). Xyleborinus saxesenii (Ratzeburg) is transcontinental in North America. Although considered by some to be an unintentional exotic introduction (i.e., Atkinson and Peck 1994), others consider it to be naturally Holarctic, with Asia, Europe, and North America in its native distribution (Wood and Bright 1992). Xyleborinus saxesenii also has been introduced into Australia, Hawaii, and South America (Argentina, Brazil, and Chile). Xyleborinus gracilis (EichhofO is native to South America and North America; in the United States, it is reported from Florida, Louisiana, North Carolina, and South Carolina (Rabaglia et al. 2006). It can be distinguished from X. saxesenii and X. alni (Niisima) by the absence of denticles on interstriae 1 and its small size (<2 mm). Xyleborinus alni, a native to Asia, was detected in North America during surveys conducted between 1996 and 1998 in the Pacific Northwest. Selected high-risk sites, such as impor-ters, warehouses, wood recyclers, mills, and other businesses in or near ports or port areas in Washington and Oregon were closely monitored using baited Lindgren funnel traps (Mudge et al. 2001). All sites were known to have received or handled imported wood or wood products.