The purpose of this paper is to homologize the sclerites of the Lepidoptera and incidentally attempt to determine to what extent these structures may be taken as Indicative of the place which the various families hold in the phylogenetic scale of classification . Much literature his been written about the thorex of a single species or family, but little or none about the group as a whole and especially with reference to the possible relationship of the families as deduced from thoracic character .