One hundred and forty-three species of Geometridae occurring in the greater Mount Mulanje area, thirty-one of which probably undescribed, are reported. This is a high number considering that only a few of the available habitats have been surveyed. Mount Mulanje, being a significantly climate changing inselberg, probably harbours a high diversity of habitats. It is argued that inselbergs, such as Mount Mulanje, allow for a diversity of micro-climatic conditions to persist. This in turn allows for the survival of a high diversity of micro-habitats, the communities of each uniquely adapted to different climatic conditions. This makes Mount Mulanje well equipped to survive future climate change and the area should be preserved at all cost.  Micro-habitat diversity is often difficult to define. It is shown that Geometridae are excellent indicators of habitat diversity.

Callioratis grandis Prout, 1922 new status (Geometridae: Diptychinae) is an extremely local species known only from the Likhubula Valley area on Mount Mulanje in Mala?i. The species was formerly treated as a subspecies of C. abraxas Felder, 1874, as the distinct male was unknown before. It is here recognised as a distinct species (new status). C. grandis can be separated from the closely related C. abraxas by the scent disseminating organs, male and female facies, male and female genitalia, LEK behaviour, early stages and DNA barcoding. These data are provided and illustrated for the first time. We consider C. grandis to be Critically Endangered (CE), using IUCN Red List criteria. The larva of C. grandis is monophagous, feeding in the wild exclusively on leaves of the Mulanje Cycad (Encephalartos gratus Prain, 1916 (Zamiaceae), a vulnerable threatened ′living fossil′ plant species that is restricted in its range. The only known colony of C. grandis, with an area of occupation of less than 10 km², is under threat from human population pressure and planned mining operations. The life history of C. grandis is described and illustrated. The known factors limiting the fundamental niche of the species are described.