Classification and Distribution of Insects, Biology tutorial

Elements of Classification:  

The naming and ordering of objects to the groups is most likely the most basic step in the growth of scientific principles.

Similarly in biology, the naming of organisms is termed to as nomenclature, and ordering them to a hierarchy of categories is termed as classification. Taxonomy comprises the theoretical basis for categorization and the study of the diversity and categorization of organisms. Categorization let us to order what we know regarding insects and to compare and contrast features. We shall anticipate members of the similar species to behave likewise in their food habits, tolerances to ecological extremes, growth patterns and other ways.

A group of identical species, put altogether in a higher category is termed as a genus, as well could be anticipated to share rather identical ecologies and to have evolved from the similar ancestors.

The categorization of organisms is mainly based on the hierarchy of categories having the most inclusive taking place at the top and the least inclusive at the bottom. Main categories employed in animal categorization are Phylum, Class, Order, Family, Genus and Species. A subclass class is generally present beneath the class category and a super family category over the family category.

  • Phylum - Arthropoda
  • Class - Insecta
  • Order - Lepidoptera
  • Family - Pyralidae
  • Genus - Ostrinia
  • Species - Ostrinia nubilalis

The scientific name of a species is binomial; it is comprised of two names, a genus name and a specific name. The species name is written above as Ostrinia nubilalis. The generic name starts by a capital letter whilst the species name starts by a small letter and both are underlined separately.

General Classification of Insects:

Insects in our environment are in plenty, some are yet unknown, even trained entomologists find it hard to identify instantly each and every insect specimen which comes their way.

There are 28 orders recognized and explained based on their features and biological properties. Out of such orders, 7 comprise the highest population of our pest problems. The list beneath starts from the most primitive insects to the most highly evolved insects.

Class Insecta:

Subclass Apterygota: primitively wingless insects 

  • Protura - Proturans
  • Collembola - Springtails
  • Diplura - Diplurans
  • Thysanura - Bristletails
  • Microcoryphia - Jumping bristletails

 Subclass Pterygota:  Winged and secondarily wingless insects.

  • Ephemeroptera - Mayflies
  • Odonata - Dragonflies and damselflies
  • Orthoptera - Grasshoppers, crickets, cockroaches and walking sticks
  • Dermaptera - Earwigs
  • Isoptera - Termites
  • Embioptera - Webspinners
  • Plecoptera - Stoneflies
  • Zoraptera - Zorapterans
  • Psocoptera - Psocids
  • Mallophaga - Chewing lice
  • Anoplura - Sucking lice
  • Thysanoptera - Thrips
  • Hemiptera - Bugs
  • Homoptera - Aphids, scale insects, cicadas, hoppers, psyllids and whiteflies.

Division Endopterygota: Complex body change all through growth 

  • Neuroptera - Alderflies, anthions, fishflies, dobsonflies, lacewings, snakeflies and owlflies 
  • Coleoptera - Beetles
  • Strepsitera - Twisted-winged parasites
  • Mecoptera - Scorpionflies
  • Trichoptera - Caddisflies
  • Lepidoptera - Butterflies and moths
  • Diptera - Flies and mosquitoes
  • Siphonaptera - Fleas
  • Hymenoptera - Ants, wasps, bees and sawflies

Subclass Apterygota:

This subclass comprises a group of the most primitive insects in orders Protura, Diplura, Collembolan, Thysanura and Microcoryplia. They are mainly wingless: they lack wings, similarly their ancestors. Internal structures which strengthen the thorax for flight in winged insects are absent. The growth exhibits little changes in form termed to as no metamorphosis.

1) Order Protura - Proturans:

They are strange insects, small (0.6 to 2.0 cm long), whitish with styled mandibles. They are deficient in antennae and eyes. Front legs came out in front of the head. They live in decomposing plant material and soil, where they nourish on fungal spores and organic debris.

2) Order Collembola - Spring Tails:

Collembola are small (0.2 to 10) mm length. They might be terrestrial or semi-aquatics. They are found most often in moist environments comprising soil, wood on forest floors and decaying leaves, at the edges of ponds. They are microscopic. The general name, spring tail comes from the furcula occurring from the underneath of the abdomen, close to the tip.

3) Order Diplura - Diplurans:

 Diplurans are whitish insects, small, blind, less than 7mm long having numerous segmented antennas. Diplurans are small in size, low profusion having secretive habits and are hardly ever seen; however often exist in soil and soil surface debris.

4) Order Thysanura - Bristletails:

They are medium-sized insects with 7 to 19 mm long having a flattened body and are mostly terrestrial, found in wood lands, beneath decaying bark, in termite nests or in mammal burrows.

The most noticeable characteristics of such insects are the two long cerci and a filament at end of abdomen which resembles a tail. A compound eye is present and scales cover the body. The most well-known species are silver fish (Lepisma saccharina).

5) Order Microcoryphia - Jumping Bristle Tails:

They look like bristletails in size and look however vary in having a cylindrical body and some abdominal styli occurring below the abdomen. They encompass big compound eyes and chewing mouthparts.

Their capability to jump (25 to 30) cm if disturbed brings up the name jumping bristle tail. They are mainly found often in wooden habitats beneath rocks, leaves and bark of decaying logs. They nourish mostly on algae and at times feed on mosses, lichens and other materials. 

Sub Class Pterygota:

These classes are characterized through possession of wings in the adult phase; a few adult Pterygota wings for illustration fleas that evolved naturally in this condition and their ancestors were reported by the possession of wings. In essence pterygotes are mainly winged however secondarily wingless.

Pterygotes comprises 25 orders, 12 of which are illustrated as follows:

1) Order I: Ephemeroptera

They are around 2,000 species and are generally termed as may-flies. The adults live for just few hours (that is, Ephemeral signifies living for a short period of time). Mayflies are soft bodied insects having big eyes. They encompass small antenna. The mouth portions of adult mayflies are atrophied. The wings are membranous having hind pair smaller than that of anterior.

2) Order II: Odonata (Dragon and Damsel Flies)

Insects in this group are much large insects having elongated bodies and very big eyes. The antennae are small and encompass strongly toothed and biting kind mouth part. Cerci are much small and encompass just one segment. The wings are membranous; each and every wing consists of a peculiar dark spot termed as pterostigma.

3) Order III: Dictyoptera

This order comprises the cockroaches and praying mantis. They include general biting mouth portion. The forewings are narrower and stouter membranous and fan-folding. The cerci are short and jointed. The styles are present in males and eggs are laid in the Ootheca.

There are two dissimilar kinds of insects in this order:

  • Cockroaches: 4,000 species
  • Mantids: 2,000 species 

4) Order IV: Orthoptera 

The word Orthoptera signifies: straight wing. The forewings are altered into tegmina which protects the membranous hind wings. The hind wings can be folded to lie at the back and altered for jumping; the femur is enlarged and accommodates the muscles for jumping. The females have well build up ovipositor. The cerci are short. A peculiar characteristic of this order is the control of special organs for making noise (or stridulatory organ).

5) Order V: Isoptera - The Termites

Illustration is Macrotermes nigeriense (Edible termites): Insects in this order are termites, soft bodied insects which live altogether in big communities. Primeval species tunnel to wood; others build large ant hills (or termitaria) build up of faeces, saliva and mud. Termites contain biting mouth parts. The two pairs of elongated wings are much alike, therefore the name Isoptera meaning equivalent wings. They are polymorphic that is, exist in various forms or castes.

6) Order VI: Siphunculata (Anoplura) -The Sucking Lice 

This group or order is a small order build up of around 300 species. The Anoplura: sucking lice are blood sucking Ectoparasites of mammals, whereas the order Malophaga includes the biting lice and are bird's ectoparasite.

Wings are absent (that is, Apterous), they have feebly grown eyes or eyes are absent. Their mouth portions are altered for piercing and sucking. There is no segmentation on the thoracic segments, come out fused altogether and the body is dorsoventrally flattened.

7) Order VII: Coleoptera (The Beetles)

This group or order is the biggest order in the animal kingdom. Coleopterans are basically terrestrial insects, found in the soil or decaying matters on soil. A few are aquatic example: Dytiscus (that is, water beetle). Most of the beetles in this order are of economic significance as they annihilate farm crops, timber and stored products. Fore wings are transformed into hard protective elytra that meet up in a line down the back. Hind wings are membranous and folded below the elytra (that is, forewings) and at times the hind wings might be absent. Mouth portions are biting kind legs.

8) Order VIII: Lepidoptera (Butterflies and Moths) 

Members are large orders of around 140,000 species and bear the name Lepidoptera as the bodies, wings and appendages are covered by pigmented scales. Adults Lepidoptera nourishes on nectar or overripe fruits and the larva are phytophagous. The mouth portions are transformed to spiral coiled suctorial proboscis.

9) Order IX: Diptera (The True-Flies) 

They are generally termed as true flies; members of this order comprise houseflies, mosquitoes, midges and sandflies. A representative characteristic of this order is presence of a single pair of membranous wings that are borne on the enlarged mesothorax. The hind wings are transformed to a pair of halters or balancers. Mouth portions are for sucking alone or for piercing and sucking. Most of them feed on nectar of flowers or decaying organic matters, illustrations comprise midges, mosquitoes and tsetse flies which particularly suck blood.

10) Order X: Hymenoptera

This order comprises bees, ants, sawflies, wasps. Members are big and around 100,000 species. They show interesting social habit, instinctive behavior, parasitism, polymorphism and communication. Wings are membranous and contain biting mouth type altered for licking and sucking.

11) Order XI: Hemiptera

They are big group of around 56,000 species, comprise of two groups:

  • Heteroptera: (true bugs)
  • Homoptera: Aphids, Cicadas and scale insects.

12) Order XII: Siphonaptera (Fleas/Aphaniptera) 

In this order, members are of small order of around 1,000 species, small wingless (that is, Apterous). A characteristic trait of this order is that, they are laterally compressed. Adult flea mouth portions are altered for piercing and sucking. They are deficient in compound eyes, however numerous species contain two ocelli on either side; most of fleas are blind. Legs are transformed for jumping and there is presence of claws for holding the host.

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