Bornean Geometridae of the subfamilies Sterrhinae (176 species in 21 genera) and Larentiinae (199 species in 56 genera) are described. For each species a diagnosis and the geographical range are given and, where known, details of habitat preference and biology. Summary lists are provided of the new taxa described (9 genera, 55 species and 2 subspecies) as well as of numerous other taxonomic changes. A checklist of all species summarises the fauna.
In an introductory section the biogeographic and ecological composition of the Bornean geometrid fauna as a whole is presented within a regional and global context. It constitutes about one quarter of the known Oriental Region fauna. The higher classification of the whole family is reviewed and a tentative phylogeny proposed.
For each subfamily, family-group names are listed and some attempt made to resolve classification at a tribal level. Two lineages are recognised within the Sterrhinae, and the tribe Trichopterygini is suggested to bear a sister-relationship to the remainder within the Larentiinae.
A final section notes errata in, and addenda to the previous two geometrid parts of the series, with description of two new ennomine species and biological notes on Naxa guttulata Warren, a fern-feeder.