Abstract Host specificity tests of Laricobius nigrinus Fender (Coleoptera: Derodontidae) were conducted under quarantine in Blacksburg, Virginia, to determine the suitability of this beetle as a biological control agent of the hemlock woolly adelgid, Adelges tsugae Annand (Homoptera: Adelgidae), in the eastern United States. Members of the genus Laricobius are known to feed on adelgids. L. nigrinus, native to western North America, was tested on three other adelgids and three non-adelgid species of Homoptera in three families. A. tsugae is an exotic insect pest of eastern ( Tsuga canadensis (L.) Carrière) and Carolina ( T. caroliniana Engelmann) hemlocks. In paired-choice and no-choice oviposition tests, L. nigrinus females preferred to oviposit in A. tsugae ovisacs over the other test species. Feeding tests showed that L. nigrinus consumed more eggs of A. tsugae than eggs of Adelges piceae (Ratzeburg) and Pineus strobi (Hartig), but not of Adelges abietis (L.). In larval development tests, L. nigrinus only completed development on A. tsugae. These results suggest that L. nigrinus has a narrow host range and that it has potential for biological control of A. tsugae. Based on these results, L. nigrinus has been cleared for field release by USDA APHIS.