INTRODUCTION

Increasing interest is being expressed worldwide in environmental studies, especially for conservation largely as a result of a serious concern that has dawned due to the present state of both local and global environmental conditions. This dawn of awareness is based on the recent realization that the state of our biological systems is of fundamental importance for the survival of human activity and also because their influence on human activity is increasing exponentially.

Each year, during the past several decades, people have been destroying enough tropical forest to cover an area the size of Pennsylvania. The geographic range of many species in the tropics is generally far smaller than it is in the temperate or polar latitudes. Thus, in the tropics, the species found in one acre differ from those in an adjacent acre far more than is the case elsewhere. During the last century, almost one half of the rainforests on earth have been destroyed. At the current rate of destruction, there will be only tiny patches of rainforest left by the middle of the 21^st century. Due to the tremendous concentration of species in the tropics and their often narrow geographic ranges, biologists estimate that tropical deforestation will result in the loss of half or more of the existing species on earth during the next 75 years. Humanity is now in the process of destroying roughly as many species during the next 50 to 100 years as were wiped out every 100 million years by natural causes. It is inconceivable that, during the coming millennia, evolution could replace with new species those lost to deforestation and other human actions.

Conservation and sustainable management requires detailed knowledge of the state of the ecosystem along with datasets that can provide information about the geographical distributions of species, environmental factors that define the resilience of ecosystems and species habitats and the processes that create or change the habitats. It’s impractical and impossible to determine all the species or sample at all the places in a particular ecosystem due to logical constraints, which necessitates monitoring taxa that are true indicators of the ecosystem. This could be achieved with the knowledge of presence and absence of certain indicator species. Also with rapid assessments being more stressed on, the need for identifying certain indicator species that can indicate the state of the ecosystem is required. Species delineated as indicator taxa (Lawton et al. 1998) or as a focal group (Di Castri et al. 1992) hence must:

1. Be easy to sample and monitor,
2. Represent diverse groups of biological significance,
3. Exhibit interrelations with diversity of other taxa and
4. Respond to changes in the ecosystem (Oliver and Beattie 1996).

Appropriate conservation strategies are to be evolved and implemented in order to maintain the existing high levels of diversity and endemism at Western Ghats. This could be achieved with inventorying, regular monitoring and management. 

Insects
Insects are virtually everywhere on the earth’s surface, excluded only by the extremes of climate at the poles and on the peaks of highest mountains; just a few species live in the sea   (Cheng, 1976). May (1990) estimates show that there are around 750000 and 790000 insect species whereas Hammond (1992) estimates show that as 950000. For the purpose of inventorying a number of 8 million insects and 8.9 million arthropods is currently used, with a world total of all the species coming to about 12.25 million (Hammond, 1992). Currently estimates ranges from 1.84 million to 50 million, with around 10 million being more favoured (Samways 1994) and quoted. Insects are numerous as individuals and species, being by far the most dominant animal biomass, genetic variety and biotic species interactors in terrestrial ecosystems. One of the intricate across-taxon interaction has been insect-plant interrelations (Samways 1994). Insects have a strong hold and a major say in most ecosystem processes, as they are pollinators and nutrient cyclers. A large number of them act as insect predators and mutualists all of which require conservation. Using insects to study how creation of mosaics, fragmentation of land, deforestation and creation of monocultures have an impact on diversity and stability of an ecosystem is a challenging and interesting task as it not only involves taxonomy of the concerned group but is also related to the behavioural aspects of the taxa under study.