Wood-pasture is one of the most iconic and exciting habitats for invertebrates in Europe, supporting numerous rare and often spectacular species. Notable among these are saproxylic beetles and flies associated with very old trees and the associated tree fungi and detached deadwood. Nearly 1800 invertebrate species are dependent on decaying wood in just Britain and Ireland alone, including about 700 species of beetles and about 730 species of flies (Alexander, 2002) and that figure is likely to rise three-or four-fold in Europe considered as a whole. In the 19th and 20th centuries, many rare saproxylic invertebrates were considered prize specimens in a collection. But in more recent decades they have started to be used increasingly as a cause célèbre for one of the biggest European countryside battles - the protection and management of veteran trees and the habitats that support them such as wood-pasture (for example Alexander and Green, 2013). The main reason for the entomological value of wood-pasture is the variety of special microhabitats associated with old trees and the large number of often highly specialised and rare invertebrate species dependent on these microhabitats (for example Speight, 1989; Harding and Wall, 2000; Alexander, 2002; Cooter and Barclay, 2006; Chandler, 2010). Collections of old trees in wood-pasture produce a plethora of microhabitats that do not, or less often, occur in younger trees and in a quantity that normal countryside with relatively few old trees cannot approach. These microhabitats include various forms of heart rot and associated fungal decay, sappy wounds, hollow trunks, rot holes of various sorts, large decaying roots, attached dead branches, loose bark, large items of detached timber, bird nests, bat roosts, hornet (Vespa crabro) nests plus the tunnels created by the larvae of beetles and the goat moth (Cossus cossus) (i.e. invertebrate microhabitats created by other invertebrates). The veteran trees of wood-pasture will often be growing in the open, which allows them to mature in a very different manner to trees in closed canopy woodland and within a very different environmental setting and management regime. This is known to affect the invertebrate fauna, with many elaterid beetles for example preferring trees in the open (Horák and Rébl, 2012), also the capricorn beetleCerambyx cerdo (Albert et al., 2012). The circumstances of wood-pasture trees also mean they are often free from the economic imperative to fell them for timber, though some may be pollarded on regular cycles. The great age of many wood-pasture trees (500-1000 years at some of the best European sites) means that these are landscape features that have had plenty of time to acquire interesting invertebrate assemblages. It effectively makes woodpastures modern refugia for once-widespread saproxylic species and assemblages - historical and ecological links to the past. Indeed, the historical and ecological continuity associated with the oldest wood-pastures probably affords a good linkage to the fully natural forests and savannahs of post-glacial Europe - landscapes that would have been far richer in old trees and the special invertebrates associated with them than most modern European landscapes. Critically, the sheer number of invertebrates associated with old trees and other habitats found in wood-pasture makes them bio-indicators of unrivalled value in helping us to understand the ecology, character, quality and conservation needs of wood-pasture. They put the spotlight on a range of microhabitats and conservation issues in a way that no other group of animals and plants can achieve, helping us to consider wood-pasture - past, present and future - in new ways and helping to define priorities. One cannot tackle biodiversity management of wood-pasture in an informed manner without reference to invertebrates. In this chapter I overview the value of wood-pastures for invertebrates. The reader will notice that this chapter is focused on flies and beetles. Moreover, rather than give an overview about the European situation, I focus on the UK. The reasons of this are threefold: 1. Beetles and flies represent the greater proportion of invertebrate biodiversity associated with wood-pasture, especially the old trees it contains.
