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Essay on Entomology
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Essay Contents:
- Essay on the Introduction to Entomology
- Essay on Fundamental Versus Applied Entomology
- Essay on Entomology as an Applied Science
- Essay on the Colossal Damage by Insects
- Essay on Entomology in India
Essay # 1. Introduction to Entomology:
The word insect has its root in the Latin word insecare (to cut into) and is equated with ‘insectum’. Entomology, the science of insects, has its origin in the Greek word temno (to cut). The Sanskrit word keet may have a similar sense and root. Thus, the most prominent physical characteristic of insects which seems to have impressed the early observers who coined these names, is the division of the insect body into 3 prominent regions, namely, head, thorax, and abdomen; this single feature has had the most spectacular impact on the etymology of entomology.
The second important character of an insect is its 3 pairs of legs; this is the basis of the term Hexapoda, meaning 6-legged, coined by Latreile in 1825 for the zoological class Insecta.
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The corresponding Sanskrit term Schatpada, also meaning 6-legged, was there in Amarkosh as early as the first century A.D. when that dictionary was compiled. The third character, which almost completes the definition of this class of animals, is the chitinous body wall, which also serves as skeleton and is called exoskeleton or outer skeleton; actually it is a characteristic of the larger group, the phylum Arthropoda, to which insects also belong.
Thus, an insect may be defined as an animal which at some stage of its development possesses the combination of these 3 major characters- (i) chitinous exoskeleton, (ii) 6 legs, and (iii) body prominently divided into head, thorax and abdomen. In other words, insects are arthropods having a combination of the last 2 characters.
In zoological classification insects constitute just one of 5 major classes of the phylum Arthropoda, which in turn is just 1 of 15 major and several minor phyla of the animal kingdom. From the economic point of view there are several groups which are important enough to have led to the development of different branches of study, such as Ornithology (birds), Ichthyology (fishes), Helminthology (worms), as well as economic departments such as those of poultry, fisheries, dairying.
There is, however, hardly any other class of animals or plants which has such vast potentialities, both for good and for bad, and such remarkable degree of even purely academic interest, as the class Insecta.
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The importance of insects consists of:
(i) The damage they cause to field crops, orchards, forests, stored products and household materials;
(ii) Their interference with man’s health and comfort;
(iii) Their value as:
(a) Pollinators and agents of fruit setting in orchards and crops,
(b) Suppliers of products like silk, honey and lac,
(c) Scavengers, and
(d) Useful parasites and predators;
(iv) Their remarkable suitability and utility as material for purely scientific studies, e.g.:
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(a) Genetics and inheritance, of which Drosophila is the hero,
(b) Sociology and population growth, for which ants, termites, wasps and bees have been in the forefront, and
(c) Adaptability, mimicry, etc., for which the leaf butterfly Kallima and the stick insect are the classical examples. All these and many others represent the diverse ways in which insects are intimately associated with man.
Essay # 2. Fundamental Versus Applied Entomology:
In practice the term entomology has an applied significance. Hence, it is necessary to understand at this stage the implications of applied science. The pairs of opposites generally used are ‘fundamental versus applied aspects’, ‘fundamental versus developmental aspects’, ‘academic versus applied approaches’. For a clear understanding, it should be divided into academic and applied aspects.
The motto of the academic approach should be, as it has always been, ‘knowledge for the sake of knowledge’. Any aspect which is not known ought to be known, irrespective of and undeterred by any idea about the utility, futility, or even harmfulness of the knowledge thus gained. Any lacuna in knowledge must be filled. This has been rightly the approach of the traditional universities.
The approach of the applied institutions, such as the agricultural research institutes or the recently established agricultural universities, has to be rather different; they have to engage themselves in problem-oriented research activities. They have to be sure that if they are successful in obtaining an information as they expect, it will be definitely useful as planned. First they have to identify the problems carefully, and then to analyse them in detail so as to expose clearly the lacunae which must be filled for proper solution of the problems.
This may call for only some adaptive research for successful exploitation of an already known principle under a specific situation, or it may call for a fundamental probe. Hence, the applied aspect should be further divided into fundamental and developmental; the former may be designated as ‘fundamentals of applied aspects’.
Alternatively, the science of entomology can first be divided into ‘fundamental and developmental aspects’, and then the fundamental aspect can be subdivided into ‘academic and applied approaches’, the former resulting from the motto ‘knowledge for the sake of knowledge’ and the latter meant to fill up a fundamental lacuna for the solution of a well-identified applied problem.
For organizational facilities and for quick scientific solutions of problems the former dichotomy is more useful, for it provides better co-ordination between developmental and fundamental aspects necessary for the solution of any problem.
Essay # 3. Entomology
as an Applied Science:
In applied biology, when the aim is economic exploitation of any species, it has to be studied in almost equal depth whether we want to exploit it in a positive or a negative way; i.e., to culture it for increasing its produce as in the case of crop plants or to check its multiplication as in the case of pest species.
The number of species of insects is so large (more than 1 million) that the preliminary item of their identification itself is one of the most tedious jobs, for which no single organization in the world is fully equipped. This is an indication of the work load involved in the solution of pest problems.
The entomologist’s interest in various forms of life has to be as varied as the insects he has to deal with, as will be evident from the following examples:
1. Class Mammalia:
The dairy, wool and livestock industries are based on this class. Monkeys, jackals, bats, squirrels and rats are serious pests of agriculture. Insects are so much responsible for diseases of man and livestock that there are separate branches of medical entomology and veterinary entomology.
2. Class Aves:
The poultry industry is based on this class. Fruit- eating birds such as parrots are serious pests, but some other birds eating insects are useful. Information on their diet and economic importance is very useful. Entomologists are also interested in insect parasites of poultry.
3. Class Reptilia:
A number of reptiles including snakes are very useful in keeping the insect pests under check.
4. Class Amphibia:
Some members of this class, e.g., frogs, are useful; they eat insects.
5. Class Pisces:
Some fishes eat insects; Haplochilus lineatus destroys mosquito larvae and has been recognized as definitely useful in the control of malaria. Ophichthy boro, which is a long, flat eel living in tidal streams, has been reported to do considerable damage by burrowing into and making wide passages across the bunds, thus connecting paddy fields containing fresh water with salt-water channels.
6. Class Chilopoda:
Centipedes feed on insects and are beneficial although sometimes they inflict very painful bites on man.
7. Class Diplopoda:
Some species of millipedes attack growing crops and become serious pests in fields and green-houses although many feed on decaying vegetable matter. Those that are pests feed on roots or leaves near the ground.
8. Class Arachinda:
The spiders (Order Araneida) feed on several injurious insects, and have venomous jaws which poison insects. Sometimes their bites cause serious results. On the whole they are beneficial.
Mites and ticks belong to the order Acarina. Some species of mites injure plants; some are parasitic on insects (locusts and grasshoppers). Some are predatory on some insects and mites. While certain species of ticks are parasitic on men, livestock and other animals, some transmit diseases.
Scorpions (Order Scorpionida) bear sting at the tip of the abdomen. They are the best known stingers. Their pedipalps are much more developed and carry a pair of pincers which are used to grasp the prey. They are predatory in habit. Despite the sting, they may be considered beneficial.
9. Class Crustacea:
Crabs, prawns, lobsters and sow bugs are sometimes injurious in greenhouses. Crabs are known to damage paddy crops, although several species are carnivorous.
10. Phylum Mollusca:
Snails and slugs are often serious pests of plants in greenhouses and in fields.
11. Class Nematoda:
Roundworms are becoming as important as plant parasites that separate departments of Nematology are coming into existence.
Essay # 4. Colossal Damage by Insects:
The one facet of insects’ life economy about which we are seriously concerned is their potentiality for doing immense harm to man’s interests. There is hardly anything that man would like to call his own and insects will not challenge his claim. Taking for example the insect damage to economic plants and plant products, a rather conservative and commonly accepted estimate has been that the average loss caused by insect pests is about 10%.
To the nation this means an annual loss of Rs.500 crore — 10% of Rs.5000 crore, which used to be our average annual income from agricultural and forest resources. The great harm done to human and livestock health is incalculable, as also its repercussion on the national activity.
In spite of their causing colossal losses in various fields of human activity, the minute size of many insects misleads us to a false sense of complacency towards insects in general. If a lion enters a town, the whole town will get thoroughly shaken up, and every effort will be made to kill it immediately, although its potentiality of damage may be only a few deaths.
But if a house fly carrying cholera germs enters a restaurant, it can flit about from dish to dish and many people may not even move their finger to scare it away, even though its potentiality for harm may be many deaths through an epidemic of cholera. The dangers from the insect world are often underestimated, and it is seldom realized that in spite of the usefulness of some groups the insects as a class constitute enemy number 1 of the human race.
It is interesting to note that there are ample references even in the most ancient records to the 3 main groups of useful insects which have been providing honey, silk, and lac; and man has preserved them for these valuable commodities. In comparison with such sound study of useful insects the knowledge about harmful insects at that time was surprisingly poor. It is amply clear from various hymns in the Vedas and other ancient literature that, although the pest problems were quite serious, the knowledge about them and their control was meagre.
In fact, realization of the dangers from the insect world has been extremely slow all over the world, and the science of entomology came into being more as a result of the hobby of amateur insect collectors than from the labours of professional economic scientists. In India this realization has been even slower, probably because of the religious beliefs and abhorrence of destroying life and certainly because of little interest in insects even as a hobby.
In this connection it is instructive to recall the Mahabharata story of sage Mandavya who developed the habit of collecting and pinning insects; for this crime he had to pay the penalty of his life by being himself impaled on the point of a crowbar. Our public is still unsympathetic to activities of entomologists and expects only simple, harmless and cheap methods of keeping away from their crops and crop produce what they would like to call mere insect nuisance. Thus, there exists a puzzling, yet interesting, anomaly.
Careful scrutiny of the whole situation suggests 2 explanations. The first is somewhat simple. The pest problems of agriculture, for example, arose with the origin of agriculture, and became aggravated with the intensification of agriculture.
Therefore, one can say that pest problems could not have been so serious when agriculture itself was in its infancy. Similarly, epidemiological studies on insects of medical and veterinary importance have shown that the incidence of insect-borne diseases increases with increase in population density of human beings and livestock.
Thus, one can also say that the harm done even by such insects might not have been so serious in the early days of human civilization. These arguments only partly explain the anomaly but provide full and convincing answer to the query why insect problems are multiplying with increase in the number of entomologists. The other subtler explanation is that insects have been exploiting their characteristic minuteness for dodging humanity and their other enemies and cutting them in a sort of complacency or false sense of security against them.
In this way the insects have been ensuring the success of their struggle for existence. Generally, however, insects are neither so minute as to be invisible to the naked eye and thus to create a sort of blind awe, nor large enough to create a visual impression about the magnitude of their seriousness, except under certain special circumstances, e.g., locust invasion.
Essay # 5. Entomology in India:
The heavy losses caused by insect pests have attracted the attention of scientists and administrators to initiate work on plant protection. The earliest available record of Indian insects is that of Linnaeus, who included 12 Indian insects in the 10th edition of his famous book System a Nature published in 1750 A.D.
However, the work on Indian insects was initiated by S.G. Koenig, a pupil of Linnaeus, in 1779 in South India. With the growing realization of the importance of insect pests, an Asiatic Society was established in Bengal in 1785. The scientific studies received greater attention and impetus with the establishment of Indian Museum at Calcutta in 1875 and the Bombay National History Society in 1883.
Since 1888, with the publication of the Journal of Bombay Natural History Society, several contributions on Indian insects were published by various workers. The most noteworthy event of this period was the starting of the publication of the Fauna of British India in 1892, published by the Government of India in London.
Further, the Indian Museum, Calcutta, published five volumes of Indian Museum Notes between 1889 and 1903. These are monumental contributions in economic entomology and may even be said to contribute the birth of applied entomology in India.
Lionel de Niceville was appointed the first Entomologist to the Government of India in 1901 with headquarters at the Indian Museum, Calcutta. He was succeeded by H. Maxwell Lefroy in 1903 and posted at Surat to study the cotton pests. In 1905, when the Imperial (now Indian) Agricultural Research Institute was established at Pusa in Bihar, Lefroy was transferred there as the first Imperial Entomologist. He published two very useful books, Indian Insect Pests (1906) and Indian Insect Life (1909).
At the same time, several State Governments also initiated entomological work, viz. Madras (1902-05), Punjab (1905) and U.P. (1906). To coordinate work in these states, separate entomologists were appointed, i.e., Coleman in Mysore (Karnataka) in 1908, T.B. Fletcher in Madras (comprising of present Tamil Nadu, Kerala and Andhra Pradesh) in 1912, M. Afzal Husain in Punjab in 1919 and P.B. Richards in U.P. in 1921.
Based on his extensive studies, T.B. Fletcher published his book Some South Indian Insects in 1914. Subsequently, several textbooks were published, among which some prominent ones are Handbook of Economic Entomology for South India by T.V. Rama Krishna Ayyar (1940, revised 1963), Textbook on Agricultural Entomology by H.S. Pruthi (1969), Insects and Mites of Crops in India by M.R.G.K. Nair (1975, revised 1986), General and Applied Entomology by K.K. Nayar, T.N. Ananthakrishnan and B.V. David (1976, latest edition 2000), Agricultural Pests of India and South-East Asia by A.S. Atwal (1976,1986), revised as Agricultural Pests of South Asia and their Management by A.S. Atwal and G.S. Dhaliwal (1997, latest edition 2015), Integrated Pest Management: Concepts and Approaches by G.S. Dhaliwal and Ramesh Arora (2001, revised 2006, latest edition 2015), Essentials of Agricultural Entomology by G.S. Dhaliwal, Ram Singh and B.S. Chhillar (2006, revised 2015), Biopesticides and Pest Management: Conventional and Biotechnological Approaches by G.S. Dhaliwal and Opender Koul (2007) Quest for Pest Management. From Green Revolution to Gene Revolution by G.S. Dhaliwal and Opender Koul (2010), and A Textbook of Integrated Pest Management by G.S. Dhaliwal, Ram Singh and Vikas Jindal (2013).
Plant protection in India got boost with the establishment of the Central Plant Protection Organization (now called the Directorate of Plant Protection, Quarantine & Storage) in 1946, under the Ministry of Agriculture, Government of India, and New Delhi. H.S. Pruthi was appointed the first Plant Protection Adviser to the Government of India. The Directorate was shifted to Faridabad in 1968.
The Directorate is functioning with the support of 31 Integrated Pest Management Centres (CIPMCs), 35 Plant Quarantine Stations (PQSs), 10 circle offices of the Locust Warning Organization, One Central Insecticides Laboratory, 2 Regional Pesticides Testing Laboratories (RPTLs) and 68 Pesticides Testing Laboratories in States/Union Territories.
At present, several agencies including the Indian Council of Agricultural Research Institutes. Directorates of Plant Protection and Extension, Government of India, State Agricultural Universities, State Departments of Agriculture, Pesticide Industries and many Non-Government Organizations (NGOs) are involved in development and implementation of IPM in various agricultural crops.
Outstanding success has been achieved in devising IPM strategies in principal agricultural crops, viz. cotton, rice, vegetables, fruits, pulses, oilseeds and plantation crops. However, much more needs to be done so that farmers are able to adopt IPM on a large scale to avoid pest-related losses and increase agricultural production.