Introduction: the need for ex situ conservation

Much conservation of insect species takes place on remnant sites where the species still occurs, with the perception that it occurred formerly more widely within the local landscape. In many cases, the target populations are very small (a few hundred or less), and loss of other populations has rendered these increasingly isolated and vulnerable. Under these conditions, on-site (‘in situ’) conservation is usually the first step contemplated, with focus entirely on the resident population and its needs. However, in addition, situations also occur when it is wise to consider one or more of (1) augmenting a field population of the insect from another source, (2) extending the species' range by creating new populations on currently unoccupied sites, and thereby reducing the risk of species extinction, and (3) ‘rescuing’ individuals or populations either to protect them from high mortality or because the site where they live is to be destroyed. These various needs, and related ones, are outlined and discussed below, as active considerations in many insect management programmes, and for which parallel needs could arise rapidly in others. In some instances, one or other of the above contexts is dictated, but in other instances some choice may be available. Thus, Rout et al. (2007) noted that practical steps in a translocation exercise may differ depending on whether the objective is to maximise population size or to maximise the number of surviving populations. Any operation of this kind may be complex and costly but, equally, may be the only or major avenue along which conservation may be pursued.