Abstract

                                Out of about seven lakhs of species of insects reported to be existing in the world with the identifications so far made only about 10,000 are known to be phytophagous (herbivorous) and of these it is only a small number of about 500 working out to a percentage of 5 that have been put under the category of major pests of some consequence to the agriculturists and horticulturists. From this we can easily infer that but for maintenance of balance-of-life by the action and reaction of forces in nature many more would have menaced us by becoming pests. The physical and biological factors evidently create a strong environmental resistance round many other insects and do not allow them to become serious pests. The climate and cultural conditions forming the physical factors and food, natural enemies and competition with others forming the biological factors not only prevent many an insect from becoming a pest but even limit its distribution in case any insect is to become a pest with the breach secured in the environmental resistance keeping it at a particular balance in its association with the other animals in the world. Therefore we owe a good deal to the environmental resistance with its physical and biological factors for keeping many insects not only within bounds but also in limiting the zones of occurrences when any of them become pests. South India had recorded about 550 insects as occurring on economic plants and of these it was not even against 100 that artificial methods of control had to be resorted to. Even then it was not everywhere and at all times of the year that the pests proved to be of serious consequence. The occurrences of pests are limited to few areas and during certain seasons. These facts go to show that nature has helped and is helping not only the agriculturists and the horticulturists but also the economie Entomologist whose work would have become quite complex and unmanageable if every phytophagous insect becomes a post.

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