Locusts

Abstract

Economic importance of locusts is well established throughout the world owing to their swarming behaviour. The damage caused by the hoppers on a small scale is mostly confined to local vegetation, primarily crops. The crop damage goes unnoticed, but they are persistent in nature and the effects they leave on planned systems, such as crop fields, are much more serious. Therefore, many taxa (genera or species) of the family Acrididae are considered as potential pests of farms, forests and even pastures. The family comprises about 10,000 species in suborder Caelifera out of a total of nearly 11,000 species. These insects exist in two polymorphic forms, solitary and gregarious. Latter form results in migratory swarms of voraciously feeding hoppers that migrate in a much coordinated fashion. Damage caused is much more apparent and extensive leading to famine-like conditions. In general, distribution of locusts and grasshoppers decreases with increasing latitudes, i.e. their occurrence increases towards the equator. These insects are polyphagous rather than being host specific and consume a variety of unrelated plant species. They are well distributed throughout the world but show significant difference in different habitats. Difference in habitat relates directly to difference in host plants because of variability in various abiotic factors of ecosystem, like altitude, latitude, precipitation, etc. Because of these facts, they are reasonably good biotic indicators of threatened habitats or ecosystems and therefore help in conservation and preservation of particular areas. In this chapter, important locust species have been included. Their diagnostic characters, life cycle, economic importance and control measures have been provided. Though these insects are important pests but natural control by climate, parasitism and predators have not been found adequate. For that reason, various artificial control measures have been suggested for their management.