Insects are ubiquitous and are found all over the world, in the Lithosphere, Hydrosphere and Biosphere. According to evidences insects appeared on this planet Earth some 440 million years ago, long before the appearance of man in this world. Because of their dynamic adaptational traits insects have escaped extinction all these years.
Insects have the innate ability to adapt themselves to any kind of adverse environmental conditions. The morphology and anatomy of insects, as well as their mode of life are quite important factors that help in the development of traits for adaptation.
In this book the authors have given a detailed account of the general aspects of insects, as well as morphology and anatomy of insects. Studies on such aspects about insects are ultimately aimed at devising and adopting physical, mechanical, chemical or biological control measures to combat the insects, which have turned into pests and pose a serious problem to mankind.
The text is substantiated with many fine, hand-drawn figures that will help better understanding of the book and make the reading more interesting.
Insects are ubiquitous, in other words they are omnipresent and are found everywhere all over the world. They are present in the highest mountain peaks, ice bergs, deep oceans, thick forests, scorching deserts, darkest caves and even in oil wells, where no other living organisms can survive. Insects possess special innate adaptations to withstand any kind of environment and so they can survive under any extremes of adverse environmental conditions and are capable of perpetuation unabated.
General Aspects About Insects ‘Insects’ are almost ubiquitous. They are found all over the world, in the icy regions of the poles, deserts, forests, mountain peaks, oceans and even in oil wells. They can adopt themselves to any climatic conditions and can live in any habitat where food is available. Insects are mostly small, air-breathing organisms of the animal world. Most of the insects live freely in nature. Many species are wild and harmless to human beings. Many are beneficial because of their role in the ecosystem. Some are a part of the food chains of wild creatures, while others through predation and parasitism hold in check many other species of insects. Insects also play a vital role in pollination. Relatively only a few species are harmful to man and are his chief competitor on earth.
The insect body is made up of multicellular tissues. The body is bilaterally symmetrical and is covered by a hard, chitinous exoskeleton. The chitin at the junction of the segments is thinner and pliable and hence insects can bend their bodies. The exoskeleton is made up of several layers of non-living cells produced from the epidermis. Because of the hard chitin us exoskeleton of the body, the growth of the insect is affected beyond a certain extent. So, to facilitate further growth,, this exoskeleton is cast off a few times and this is known as ‘molting’. The number of moultings in a particular species is more or less constant.
Similar to animals of the higher order, insects also possess all important internal systems of organs necessary for the proper performance of the various vital functions. The most important of the systems are the alimentary or digestive system, the circulatory system, the respiratory system, the reproductive system and the excretory system. The fundamental arrangement of the various organs is more or less similar in all insects and does not exhibit much remarkable variations as seen in the external morphological features. The dorsal blood vessel or heart runs along the median line immediately below the dorsal wall. The digestive system including the alimentary canal and its appendages lie in the middle, below the heart. The nervous chain lies below the alimentary canal and immediately above the ventral wall.
Insects generally reproduce by laying eggs or ‘ova’. The initiation of growth inside an egg, which in most cases is preceded by fertilization, leads to a long series of changes, finally attaining the adult stage and in due course to sexual maturity and finally to reproduction of a new generation. This chain of events from the egg stage to adult constitutes the ‘life history’ or ‘life cycle’ of an insect.
Classification of Living Organisms The classification of living organisms has passed through several changes and has reached the present stage with the gradual assimilation of more and more knowledge about them. The classification is mainly based on the morphology, anatomy, life style, habits, habitats, metamorphosis and such other characteristics. Though the concept of classification of living organisms was perhaps started by Aristotle between 384 - 322 BC, it was the Swedish Scientist Carl Linnaeus (1788), who presented the classification, which was acceptable to most of the Taxonomists. He propounded the binomial nomenclature of naming each and every organism of animal and plant origin with a genetic and species name. In his classification he was consistent in using Latin names for all the organisms.
