Trechini beetles : Trechini are small- to medium-sized ground beetles that require high humidity. Almost half the known New Zealand trechine species are found in caves, which provide an environment close to 100% humidity, and these are highly modified for an underground life. Insects that are restricted to caves have had an interesting history as they have had to cope with major geological changes to the landscape over the last few million years. Surface-dwelling species also require high humidity and are usually found along streamsides or in beach gravel below the high water mark. There are about 2500 species in the tribe Trechini worldwide. Currently there are 33 species of trechines known from New Zealand, all of which are endemic except one. Amongst New Zealand's relatively few species are some lineages that are apparently not present in Australia, Tasmania, or South America, giving rise to some interesting biogeographic questions. Although the number of New Zealand's trechine species is small on a world scale, they are a special part of our biota because they are one of our most diverse groups of cave insects, they occupy unusual habitats, and they show extreme adaptations to the hostile environments in which they live. In this Fauna New Zealand Carabidae of the tribe Trechini are revised and relationships to the world fauna are discussed. Their survival during changing geological episodes is discussed.
