In 1991, Microctonus hyperodae Loan (Hymenoptera: Braconidae, Euphorinae), collected from eight diverse South American locations, was released in New Zealand as a biological control agent of the pasture pest Listronotus bonariensis (Kuschel) (Coleoptera: Curculionidae). Equal numbers of each South American geographical population of this thelytokous endoparasitoid of adult hosts were released in New Zealand. A morphometric method described in this paper provided a means of classifying M. hyperodae adults as originating from either east or west of the Andes. Analysis revealed that, on average, specimens collected in Chile had significantly more antennal segments, narrower stigmas and longer radial cells than those collected in Brazil, Uruguay and Argentina. Significant differences between populations originating from each side of the Andes were also recorded in the dimensions of metasomal tergum one and basitarsus three. The morphometric method should, therefore, assist in defining the origins of M. hyperodae established in New Zealand. This information will be used in attempts to ascertain the importance of climate matching and host-parasitoid co-evolution to the outcome of the L. bonariensis biological control programme. none