The monophyly of the Geometrinae is examined by investigating the green wing pigment and morphology of the tympanal (hearing) organs. The green colour of Geometrinae is caused by a single pigment, here termed geoverdin, located in the scales. Analysis of this pigment indicates that it is neither a bile pigment nor a derivative of chlorophyll. A method developed for taxonomic comparison of lepidopteran pigments and based on a chromatographic profiling technique is presented. The morphology of geometrid tympanal organs is described and an apomorphy for the Geometrinae, the distinctive shape of the ansa, is proposed. The value of the taxonomic literature on the Geometrinae is assessed in terms of its ability to identify internal monophyletic groups. A taxonomic revision of the genus Oospila Warren is presented, in which the neotropical genera Auophylla Warren, Auophyllodes Prout, Halioscia Warren, Oospila Warren, Oospiloma Prout, Progonodes Warren and Racheolopha Warren are united into a single genus. Phylogenetic analysis is used to demonstrate the monophyly of the revised genus Oospila and to assess relationships between species groups within it. The revised genus Oospila is defined as a monophyletic group supported by two apomorphic characters: the form of the abdominal crests and the presence of an anellar complex produced by the fusion of the juxta and transtilla. Sixty-six species of Oospila are treated, of which three are described as new. One new subspecies is also described. Forty-eight species group names are synonymised, and 16 species are recombined with Oospila.

The Geometrid moth genus Erilophodes Warren was redefined, using morphological characters of the wings, abdomen, hind tibiae and genitalia. Two new species, E. Spinosa and E. toddi, were described on the basis of male characteristics. Females of these species are indistinguishable from each other and from those of E. colorata Warren, the type species. Ischnopterix Wagneri Le Moult was treated as a junior subjective synonym of E. colorata Warren. Three species referred to Erilophodes Warren were removed from the genus. E. indistincta Warren was transferred to the genus Ischnopterix Hubner. E. marmorinata Bastelberger was placed as a junior subjective synonym of Neodesmodes semialbata Warren. E. arana (Dognin) was transferred to the genus Neodesmodes Warren. Erilophodes Warren was found to occupy an area from Espirito Santo on the southern coast of Brazil to Montevideo, Uruguay, westward through the northeastern tip of Argentina into southeastern Paraguay. There seems to be considerable overlap in the ranges of the three species. Placement of Erilophodes Warren in the subfamily Ennominae was verified. With some reservations the genus was retained in the tribe Nacophorini. / Master of Science