Ecology or the relationship of organisms to their environment has in recent years developed into a major biological discipline embracing within its field other disciplines as well. In recent years tendency has been to emphasize the various aspects of ecology from the angle of ecosystem and much stress has been laid on the conservation of natural fauna and flora.The relationship between man and insects dates back since time immemorial. Insects are foes and friends and have always been the subject of interest to human beings. The part played by the insects in any ecosystem, the hazards caused by them and the interest in conserving the beneficial ones form the general theme of the work. Various ecological aspects by taking insects as key animals has been discussed and it is hoped that the book would attract wide attention of students, teachers, researchers and persons involved in environmental as well as integrated pest management.