The geometrid subfamily Larentiinae is represented in the Nearctic Region by approximately 400 species assigned to 60 genera in 8 tribes. A number of the species are of economic importance. Some of these defoliate trees and ornamental shrubs and others feed on the seeds of conifers. There are also many species which may be collected in samples of foliage-feeding insects and in order to complete the records on such samples it is necessary to identify them. Information on characters for the identification of genera and species is quite scarce for the larval Larentiinae. To fill such a need the present study arose.
This study has been divided into two parts, the first to deal with the comparative external morphology and classification, and the second to serve as an identification guide and descriptive catalogue of the larval species.