The genus Allotropa is in the subfamily Sceliotrachelinae of the family Platygastridae (Masner & Huggert 1989). The members of Allotropa are known as primary endoparasitoids of various mealybugs (Masner & Huggert 1989; Vlug 1995). Twenty-one species are described from all major biogeographic regions of the world, with five species described from the Nearctic region (Muesebeck 1979). The mealybug Oracella acuta (Lobdell) was accidentally introduced into Guangdong Province, China in 1988 (Sun et al. 1996). Due to a lack of natural enemies, the mealybug spread rapidly through stands of slash pine, Pinus elliotti Englm. (Zhou et al. 1994), causing severe growth loss (Ren et al. 2000). After failed attempts to find native natural enemies in China, a Sino-U.S. forestry cooperative project was initiated to study the parasitoid complex of O. acuta in the U.S. and to evaluate the potential for a classical biological control program against the mealybug in China. Three primary endoparasitoids of O. acuta were identified: Zarhopalus debarri Sun (Encyrtidae), Acerophagus coccois E. Smith (Encyrtidae), and one in the genus Allotropa (Clarke et al. 1990, 1992; Sun et al. 1998). This plastygastrid was identified by one of the authors (L.M.) as a species new to science. Due to its potential inclusion in a biological control program, a description of this species is undertaken. New character states were used in this description because those traditionally used in taxonomy of Allotropa offered only limited value in species discrimination. Among the new character states used were the morphology of the mesopleuron, the pilosity of the metapleuron, and the microsculpture of the mesoscutum. The mesopleuron offered excellent distinguishing character states, such as the shape of the mesopleural depression, and the presence or absence of a sternaulus or of deep pits. In contrast to the glabrous mesopleuron, the metapleuron is typically hairy in most, but not all species. The microsculpture of the mesoscutum offered useful diagnostic character states in most species. Since the character states above were not considered in previous descriptions, types of all species were re-examined for confirmation.