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Classification involves grouping organisms into a series of hierarchical categories. Actual method of establishing a classification consists in defining groups or categories on a hierarchical scale. The animals can be classified in a taxonomic hierarchy consisting of a series of categories of ascending ranks from species to kingdom. Each of these categories includes one or more groups from the next lower level. Therefore, all animals can be classified in a taxonomic hierarchy consisting a series of categories in ascending order from species to kingdom such as species, genus, family, order, class, phylum and kingdom.

According to the history of biological classification, Aristotle, a Greek philosopher classified different animals based on the habitat, characteristics etc. Later Swedish botanist Carolus Linnaeus introduced taxonomic hierarchy categories during 18th century and this system is followed globally.

Taxonomic hierarchy refers to the sequence of categories in increasing or decreasing order. Kingdom is the highest rank and species is the lowest rank in hierarchy. Taxonomic hierarchy is the process of arranging various organisms into successive levels of biological classification. Each of the level of the hierarchy is called taxonomic category or rank.

Code of Ethics was observed by International Commission on Zoological Nomenclature for renaming of homonyms. The commission had issues declarations or opinions from time to time, which together constitute the start of a code of ethics in the field of nomenclature. The first Declaration of the international Commission was as follows:

• When it is noticed by any zoologist that the generic name or specific name published by any living author as new is in reality a homonym, and therefore unavailable under articles 34 and 36 of the Rules of Nomenclature, the action is for said person to notify the said author of the facts, and give said author an opportunity to propose a substitute name.

• When the author of a newly discovered generic or specific homonym is dead, the discoverer is free to rename the genus or species as he likes. It is common practice to rename the category after the author of the homonym. However, this practice was never universal and it is not a matter of ethics.

Taxonomic keys are devices that make identification of taxa easy and enjoyable. A key is presentation of appropriate diagnostic characters in a series of attractive choices to facilitate identification of a specimen.

Key characters are the characters that are easily perceived of very low variability, usually present in preserved material. They are useful as convenient labels for distinguishing taxa by the process of classification. Many taxonomic characters such as chemical, chromosomal, physiological and behavioural may have high value of identification because they are inaccessible in preserved material. Ideal key characters apply equally to all individuals of the population. They are absolute, relatively constant and external so that they can be observed directly without special equipment.

Identification of the insects is the integral part of systematics. It utilises all taxonomic procedures. The collections in the world are the accumulation of past taxonomists and are stored for the future identifications. Every species name is based on a published description or figure and usually on the type specimen. Identification is the association of other specimens with the appropriate description or with type specimen.

The steps in identification are as follows:

1. Preliminary key to orders and families

2. Key to genera and species if recent monographs or faunal works are available

3. Reference to the most recent catalogues

4. Reference to current bibliographies for literature published subsequent to the most recent catalogues

5. Reference to original descriptions

6. Comparison with the authentic described specimens or with types.

Super Species

According to Mayr (1931, 1942) Linsleg and Usinger (1953),“A super Species is a monophyletic group of very closely related and largely or entirely allopatric Species”.

Super species are, in other words, groups of populations that seem on other grounds (morphology, ecology etc.) to have passed beyond the point of potential interbreeding and to have acquired separate evolutionary roles. They are so by the more conclusive evidence of remaining separate when sympatric. It is to be assumed that they are still near the critical point of specification, near a definitive isolation. They are nascent species that will, if they survive, collectively form a subgenus or eventually a genus but have hardly get reached that degree of divergence.

They are not given special names; the Rules of Nomenclature make no provision for that usual designation and they are mostly known by the name of an included species and are in fact super species.

The Species Concept in Systematics

The modern biological or, more strictly, genetical concept of a species is a group of interbreeding organisms, genetically isolated from other such groups. The definition of the category species has long been one of the major problems of taxonomy. It is because of two reasons:

1. Because of the congruity of lingering typological concepts with the nature of evolving species.

2. Because evolutionary species may have changing characters and are only gradually differentiated in phylogeny.

For evolutionary study and descriptive purposes, many kinds of variation within species come in to consideration, but the only regular intra specific taxon is the subspecies. Subspecies are widely but not universally useful and their definitions yield to the same sort of criteria as for dividing other phylogentic continuance.

Man has tendency to classify everything in a hierarchical manner for example, ships may be classified on size, weight, what they carry or naval versus merchant or passenger. Any of these classification is as valid as any other.

But classification of biological species is unusual in that a predefined system exists i.e. the evolutionary relationships among organisms. But evolutionary relationships can only be estimated; and contrary to popular belief, even a good fossil record does not conclusively show the phylogeny or evolutionary tree of a group species.

Numerical taxonomy can be defined as “Numerical evaluation of the affinity or similarity between taxonomic units and ordering of these units into taxa on the basis of their affinities”. The term includes drawing of phylogenetic inferences from the data by statistical or other mathematical methods to the extent to which this should prove possible. The practice involves a number of fundamental assumptions and philosophical attitudes toward taxonomic work.

The science of taxonomy started with Linnaeus, who used two Latin names for an organism by a universally agreed name and identity, and further provided means for their realistic classification. These identifications and classifications got strengthened further with accumulated biological knowledge. In the recent times taxonomy has become more demanding subject for areas in entomology, which are dependent on access to accumulated experience and knowledge for their survival and development. By providing name and classifying an insect, taxonomy provides information on the nature of population, life cycle, habitat and behaviour and thereby developing hypotheses, concepts and theories, which are basic to biological control. In addition, it enables comparison and synthesis, all of which lead to refinement and fine tuning of the concepts and theories for identification.

Origin of systematics is as old as Vedas (1500 BC), Ramayana (1900 BC), Mahabharat (1400 BC) and Upanisad (350 BC) in which mention had been made about various animals.

History of Insect Classification

Linnaeus (1758-1766) in the 12th edition of Systema Naturae, divided insects into 9 orders

1. Coleoptera (earwigs – Dermeptera).

2. Orthoptera.

3. Hemiptera.

4. Lepidoptera.

5. Neuroptera (ant lion, Sialis, termites and dragon flies).

6. Hymenoptera

7. Diptera.

8. Thysanoptera.

9. Aptera (wingless insects, spiders, scorpions, terrestrial crustacians and Myriapods).

The foundation of modern insect classification was laid by Brauer in 1885. According to Brauer insects were classified as Subclass: Apterygogenea (pterous) and Pterygogenea (winged) based on:

• Presence or absence of wings.

• Mouthparts.

• Metamorphosis.

• Number of Malpighian tubules.

• The nature of wings.

• Thoracic segments etc.

The earliest classification of insects was based on habits and habitats and on certain gross anatomical features that define the general aspects of different kinds. In classifying insects, not only anatomical characters but also facts pertaining to physiology, biology, distribution, ecology and sometime cytology of the species is taken into consideration.

Classification

Classification is ordering of organisms into groups (or sets) on the basis of their relationships that are of associations by contiguity, similarity or both.

Classification of living things is an attempt to interpret nature. It attempts to bring together the kinds that are alike and closely related and to separate those that are unlike and unrelated.

Animals might be classified in various ways but the classification is based primarily on structural characters. Those animals with certain structures in common are classified into one group, and those with other structures into other group. Thus the animal kingdom is divided into a dozen or so major groups called phyla (singular, phylum); each phylum has a name, and its members have certain structural characters in common. The characters used to distinguish phyla include the number of cells, symmetry, body form and segmentation, the nature of the appendages, and the arrangement of the internal organs.

On the basis of degree of complexity, and probably evolutionary sequence, the animal phyla are usually arranged in a series from the lower phyla to the higher ones.

Nomenclature should not be confused with terminology which deals with terms, like antenna, abdomen, radius etc. Names of animal and plants may be either vernacular or scientific.

Vernacular names or local names of plants and animals are different from region to region, from language to language.

Scientific names or Latin or International names are used universally all over the world. Without them we would not be able to communicate and to use the knowledge accumulated about animals and plants in literature. These international names are under certain rules or nomenclature.

Nomenclature

No-men-cla-ture means a system of names. It is derived from Latin Nomen means name and calor means to call, which means to call by names. Nomenclature is the “language of Zoology” and the rules of nomenclature are its grammar. Since all zoologists work with animals and used their names, it is essential that the general principles of zoological nomenclature be familiar to all zoologists.

Origin of Insects

Insects are highly specialized group of invertebrates belonging to the largest animal Phyla, the ARTHROPODA, which also includes in it, the prawns, crabs, lobsters, centipedes, millipedes, scorpions, ticks, mites and spiders. Practically three fourth of the animal species come under this phylum.

The Arthropods evolved during Cambrian period from primitive annelidan ancestor. The main evolutionary stem of Arthropod is represented by the Crustacia- Insecta- Myriapoda.

The insects originated in the Devonian period of Palaeozoic era. Diplura and Thysanura are the most primitive wingless insects while mayflies, damselflies, dragonflies and stoneflies represent the primitive winged insects.

Evolution

Evolution is a process whereby population are altered over a period of time and may split into separate branches, hybridize together or terminate by extinction.

Arthropods occur up to the height of over 6,080 meters on land and up to the depth of about 59,728 meters in water. Different arthropod species are adapted for living in air, on land, in soil and in fresh, brackish or salt water.

Many insects are economically important for being pests of crops, stored grains, stored food, household goods and clothing etc. Some insects and arachnids are in one way or the other responsible for certain diseases of crops, domestic animals and human beings. Some arthropods, on the other hand, such as crabs, lobsters, prawns and shrimps form a part of human diet while, small sized crustaceans are staple food for fishes. Many parts of the world have witnessed some insects and spiders eaten by many land animals including man.

Insects share many characters with other arthropods, but the other arthropods have not been able to exploit these to the extent insects have evolved. The presence of functional wings is a very important character which insects do not share with other arthropods, that is why insects have distinct advantage over other arthropods in their struggle for existence and dominance. A comparative account of Insecta and other arthropod classes is given in Table 1.

Origin of Systematics

In Vedas (1500 BC), Ramayana (1900 BC), Mahabharata (1400 BC), and Upanishad (350 BC) mention had been made about various animals. The number of known species of animals is much greater than that of plants and has been estimated at about more than one million. When subspecies are included, the number may double to more than two million named forms of animals. The new animals are being described at the rate of about 10,000 per year. Metcalf (1940) estimated that one and a half million species names are already applied while Silvestre (1929) calculates an estimated 3 million probable species of insects.

Systematics

Systematics is a term coined by a Swedish naturalist Linnaeus (Systema Naturae 1735) which is a Latinized Greek word Systema, as applied to the systems of classification. According to Simpson, “Systematics is the scientific study of the kinds and diversity of organisms and any or all relationships among them.” It includes Taxonomy, identification, classification and nomenclature. Now-a-days, both terms are used inter-changeably in the fields of plant and animal classification.

Arthropod life began very early in Palaeozoic region, about 600 million years ago in the sea. The arthropod foundations were laid with the evolution of metamerism in segmented worms, and in the ancestral arthropods it resembled the now extinct Trilobites. They had harder cuticle forming the exoskeleton and a pair of jointed legs with each of its metameric segments.

The Trilobite stock soon diversified into:

a) Chelicerates.

b) Mandibulates.

a) Chelicerates: In Chelicerates, the anterior body segments fused to form the prosoma, bearing a pair of chelicerae, the feeding organs; a pair of pedipalps and four pairs of walking legs. The remaining segments formed the legless opisthosoma. This gave rise to Eurypterids (Extinct) Xiphosurians, Pycnogonids and the highly successful Arachnids, including the scorpions, spiders, ticks and mites.

The name Lepidoptera derived from the Greek words “lepido” meaning Scale and “ptera” meaning wings refers to the flattened hairs (Scales) that cover the body and wings of most adults. Lepidoptera (Moths and Butterflies) is the second largest order (1.10 lakh sp.) in the class insecta, characterized by the body, wings and appendages being generally covered densely with pigmented scales which provide the colour pattern of the characteristic of the species and play an important role in courtship and intraspecific recognition.

Adults

• Head: Hypognathus and relatively small.

• Compound eyes are large and set well apart. Ocelli two in number in moths or reduced to Chaetosoma in butterfly.

• Mouthparts form a coiled tube (Proboscis) beneath the head.

• Antennal type:

• Butterflies: Clubbed, clavate, capitate.

• Moths: Pectinate (Uni/Bi).

• Adults have siphoning type mouthparts except in micropterygidae (Mandibulate mouthparts). Front wings large, triangular, hindwings large, fan shaped.

• Body and wings covered with small, overlapping scale.

• Thoracic segments are fused and metathorax is the largest and most prominent.

• Wings covered with scales. Androconia (Plumules) on upper surface of wings in some males serves as outlet for odouriferous glands. are fringed distally with each tip finely divided. • Wing coupling apparatus variable (generally Frenulum and retinaculum or Amplexiform type)

• The name Zoraptera, derived from the Greek “zor” meaning pure and “aptera” meaning wingless was given to the order before winged forms were discopvered.

• Members of the order Zoraptera are small (less than 4 mm) and usually found in rotting wood, under bark or in piles of old sawdust.

• They live in small aggregations (gregarious) and appear to scavenge on spores and mycelium of fungi, or occasionally, on mites and other small arthropods.

• polymorphism in populations; with blind, apterous individuals dominating during colony life, but populations produce eyed alates (individuals with wings) for dispersal and founding new colonies.

• males with a distinctive “mating hook” and unique mating behaviors.

• unique grooming behaviors

Adults

• Antennae 9-segmented (moniliform).

• Mouthparts mandibulate, hypognathous.

• Soft bodied, small (usually less than 3 mm).

• Wings often absent with reduced venation when present.

• Tarsi 2-segmented

• Cerci 1-segmented

• ovipositor absent

• incomplete development (egg, nymph, adult)

Apterygotes

The Apterygota, which formerly included the other primitively wingless insects currently placed in the class Entognatha, are now restricted to the two orders Archaeognatha and Zygentoma, which in turn were formerly united as the Thysanura. Despite the superficial similarity of the two groups, it is now clear that they are not closely related, mainly because of fundamental differences in the mouthparts. The Archaeognathous mandibles are monocondylic, having a single articulating point with the head so that the mandible can rotate. The Zygentomous mandibles are dicondylic, with two articulating points that restrict the motion to a single plane yet enable the development of a much stronger biting action; this is the type found in all the higher insects, and the Zygentoma may well be the sister group of the Pterygota, or winged insects. Clearly the ‘Apterygota’ is not a monophyletic group and is simply retained for convenience in grouping these two orders that superficially resemble each other and have similar life histories.

History

• Aristotle (384-322 BC): A good beginning of taxonomy was made by Aristotle (Historia Animalium). He erected entomon. He could distinguish mandibulates and haustellates; winged and wingless forms. The insect orders like coleopteran, dipteral, psyche (Lepidoptera) were created by him. Hence, he was called as Father of Biological Classification.

• Linnaeus (1707-1778): Father of Taxonomy and Binomial Nomenclature. He coined the term Insecta. He used the term Systematics. His greatest contribution is Systema Naturae.

• Brawer (1885): Laid foundations for modern system of classification and responsible to divide class Insecta into Apterygota and Pterygota.

• Michael Anderson (1727-1806): Contemporary and rival of Linnaeus. Introduced Numerical Taxonomy and hence is called Father of Numerical Taxonomy. 

• Johan Christian Fabricius (1745–1808), the first systematist considered to specialize on insects, published in 1778 his Philosophia Entomologica (40), the first textbook of entomology.

• Fabricius had already set forth his system of insects in 1775 (Systema Entomologiae), his system of genera in 1776 (Genera Insectorum), and then numerous works on species, culminating in individual accounts of the species of each order