File Name: introduction to insect biology and diversity .zip
Insects or Insecta from Latin insectum are pancrustacean hexapod invertebrates and the largest group within the arthropod phylum. Definitions and circumscriptions vary; usually, insects comprise a class within the Arthropoda. As used here, the term Insecta is synonymous with Ectognatha.
Insects or Insecta from Latin insectum are pancrustacean hexapod invertebrates and the largest group within the arthropod phylum. Definitions and circumscriptions vary; usually, insects comprise a class within the Arthropoda.
As used here, the term Insecta is synonymous with Ectognatha. Insects have a chitinous exoskeleton , a three-part body head , thorax and abdomen , three pairs of jointed legs , compound eyes and one pair of antennae. Insects are the most diverse group of animals; they include more than a million described species and represent more than half of all known living organisms. Nearly all insects hatch from eggs. Insect growth is constrained by the inelastic exoskeleton and development involves a series of molts.
The immature stages often differ from the adults in structure, habit and habitat, and can include a passive pupal stage in those groups that undergo four-stage metamorphosis. Insects that undergo three-stage metamorphosis lack a pupal stage and adults develop through a series of nymphal stages. The most diverse insect groups appear to have coevolved with flowering plants. Adult insects typically move about by walking, flying, or sometimes swimming.
As it allows for rapid yet stable movement, many insects adopt a tripedal gait in which they walk with their legs touching the ground in alternating triangles, composed of the front and rear on one side with the middle on the other side.
Insects are the only invertebrates to have evolved flight, and all flying insects derive from one common ancestor. Many insects spend at least part of their lives under water, with larval adaptations that include gills , and some adult insects are aquatic and have adaptations for swimming. Some species, such as water striders , are capable of walking on the surface of water.
Insects are mostly solitary, but some, such as certain bees , ants and termites , are social and live in large, well-organized colonies. Some insects, such as earwigs , show maternal care, guarding their eggs and young. Insects can communicate with each other in a variety of ways. Male moths can sense the pheromones of female moths over great distances. Other species communicate with sounds: crickets stridulate , or rub their wings together, to attract a mate and repel other males.
Lampyrid beetles communicate with light. Humans regard certain insects as pests , and attempt to control them using insecticides , and a host of other techniques. Some insects damage crops by feeding on sap, leaves, fruits, or wood. Some species are parasitic , and may vector diseases. Some insects perform complex ecological roles; blow-flies , for example, help consume carrion but also spread diseases.
Insect pollinators are essential to the life cycle of many flowering plant species on which most organisms, including humans, are at least partly dependent; without them, the terrestrial portion of the biosphere would be devastated. Silkworms produce silk and honey bees produce honey and both have been domesticated by humans.
The word "insect" comes from the Latin word insectum , meaning "with a notched or divided body", or literally "cut into", from the neuter singular perfect passive participle of insectare , "to cut into, to cut up", from in - "into" and secare "to cut";  because insects appear "cut into" three sections.
The precise definition of the taxon Insecta and the equivalent English name "insect" varies; three alternative definitions are shown in the table. In the broadest circumscription , Insecta sensu lato consists of all hexapods. A narrower circumscription restricts insects to those hexapods with external mouthparts, and comprises only the last three groups in the table.
In this sense, Insecta sensu stricto is equivalent to Ectognatha. Insecta sensu strictissimo is then equivalent to Pterygota. Hexapoda Insecta, Collembola , Diplura , Protura. Crustacea crabs , shrimp , isopods , etc.
Arachnida spiders , scorpions , mites , ticks , etc. A phylogenetic tree of the arthropods and related groups . Although traditionally grouped with millipedes and centipedes —possibly on the basis of convergent adaptations to terrestrialisation  —evidence has emerged favoring closer evolutionary ties with crustaceans. In the Pancrustacea theory, insects, together with Entognatha , Remipedia , and Cephalocarida , make up a natural clade labeled Miracrustacea within Crustaceans, now termed Pancrustacea.
Insects form a single clade, closely related to crustaceans and myriapods. Other terrestrial arthropods, such as centipedes , millipedes , scorpions , spiders , woodlice , mites , and ticks are sometimes confused with insects since their body plans can appear similar, sharing as do all arthropods a jointed exoskeleton. However, upon closer examination, their features differ significantly; most noticeably, they do not have the six-legged characteristic of adult insects.
The higher-level phylogeny of the arthropods continues to be a matter of debate and research. In , researchers at Tufts University uncovered what they believe is the world's oldest known full-body impression of a primitive flying insect, a million-year-old specimen from the Carboniferous period. Four super radiations of insects have occurred: beetles from about million years ago , flies from about million years ago , moths and wasps both from about million years ago.
The flies and moths along with the fleas evolved from the Mecoptera. The origins of insect flight remain obscure, since the earliest winged insects currently known appear to have been capable fliers. Some extinct insects had an additional pair of winglets attaching to the first segment of the thorax, for a total of three pairs. As of , no evidence suggests the insects were a particularly successful group of animals before they evolved to have wings. Late Carboniferous and Early Permian insect orders include both extant groups, their stem groups,  and a number of Paleozoic groups, now extinct.
This gigantism may have been due to higher atmospheric oxygen levels that allowed increased respiratory efficiency relative to today. The lack of flying vertebrates could have been another factor. Most extinct orders of insects developed during the Permian period that began around million years ago. Many of the early groups became extinct during the Permian-Triassic extinction event , the largest mass extinction in the history of the Earth, around million years ago. The remarkably successful Hymenoptera appeared as long as million years ago in the Triassic period, but achieved their wide diversity more recently in the Cenozoic era, which began 66 million years ago.
A number of highly successful insect groups evolved in conjunction with flowering plants , a powerful illustration of coevolution. Many modern insect genera developed during the Cenozoic. Insects from this period on are often found preserved in amber , often in perfect condition.
The body plan, or morphology , of such specimens is thus easily compared with modern species. The study of fossilized insects is called paleoentomology. Panephemeroptera Mayflies. Grylloblattodea ice-crawlers. Mantophasmatodea gladiators. Trichoptera Caddisflies. Neomecoptera winter scorpionflies.
Cladogram of living insect groups,  with numbers of species in each group. Traditional morphology-based or appearance-based systematics have usually given the Hexapoda the rank of superclass ,  : and identified four groups within it: insects Ectognatha , springtails Collembola , Protura , and Diplura , the latter three being grouped together as the Entognatha on the basis of internalized mouth parts. Supraordinal relationships have undergone numerous changes with the advent of methods based on evolutionary history and genetic data.
A recent theory is that the Hexapoda are polyphyletic where the last common ancestor was not a member of the group , with the entognath classes having separate evolutionary histories from the Insecta. The following represents the best-supported monophyletic groupings for the Insecta.
Insects can be divided into two groups historically treated as subclasses: wingless insects, known as Apterygota, and winged insects, known as Pterygota. The Apterygota consist of the primitively wingless order of the silverfish Zygentoma. Archaeognatha make up the Monocondylia based on the shape of their mandibles , while Zygentoma and Pterygota are grouped together as Dicondylia.
The Zygentoma themselves possibly are not monophyletic , with the family Lepidotrichidae being a sister group to the Dicondylia Pterygota and the remaining Zygentoma. Paleoptera and Neoptera are the winged orders of insects differentiated by the presence of hardened body parts called sclerites , and in the Neoptera, muscles that allow their wings to fold flatly over the abdomen.
Neoptera can further be divided into incomplete metamorphosis-based Polyneoptera and Paraneoptera and complete metamorphosis-based groups. It has proved difficult to clarify the relationships between the orders in Polyneoptera because of constant new findings calling for revision of the taxa.
For example, the Paraneoptera have turned out to be more closely related to the Endopterygota than to the rest of the Exopterygota. The recent molecular finding that the traditional louse orders Mallophaga and Anoplura are derived from within Psocoptera has led to the new taxon Psocodea. The Exopterygota likely are paraphyletic in regard to the Endopterygota.
Matters that have incurred controversy include Strepsiptera and Diptera grouped together as Halteria based on a reduction of one of the wing pairs—a position not well-supported in the entomological community. Fleas are now thought to be closely related to boreid mecopterans. The study of the classification or taxonomy of any insect is called systematic entomology. If one works with a more specific order or even a family, the term may also be made specific to that order or family, for example systematic dipterology.
Insects are prey for a variety of organisms, including terrestrial vertebrates. The earliest vertebrates on land existed million years ago and were large amphibious piscivores. Through gradual evolutionary change, insectivory was the next diet type to evolve. Insects were among the earliest terrestrial herbivores and acted as major selection agents on plants. Many insects make use of these toxins to protect themselves from their predators. Such insects often advertise their toxicity using warning colors.
Over time, this has led to complex groups of coevolved species. Conversely, some interactions between plants and insects, like pollination , are beneficial to both organisms. Coevolution has led to the development of very specific mutualisms in such systems.
Estimates on the total number of insect species, or those within specific orders , often vary considerably. Globally, averages of these estimates suggest there are around 1. With only , known non-insects, if the actual number of insects is 5. As only about 20, new species of all organisms are described each year, most insect species may remain undescribed, unless the rate of species descriptions greatly increases. Of the 24 orders of insects, four dominate in terms of numbers of described species; at least , identified species belong to Coleoptera , Diptera , Hymenoptera or Lepidoptera.
As of , at least 66 insect species extinctions had been recorded in the previous years, which generally occurred on oceanic islands.
An insect is any kind of bug. It is this method of 'breathing' which stops insects from getting very large. Robert Lee Metcalf was an American entomologist, environmental toxicologist, and insect chemical ecologist. Some insects destroy other insects that are considered harmful. Download full-text PDF. Mary Kay Malinoski. Entomology pliesch wisc.
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The practice of rice crop cultivation will affect the trophic structure and the diversity of insects that are formed. One of the common cultivation practices carried out by farmers was the control of pests by using pesticides. This study aimed to find out which pest management strategies that are effective in maintaining environmental health and understanding how natural enemies were affected by the application of synthetic pesticides. The first treatment was paddy field with integrated pest management IPM , the second treatment was conventional rice field with a technique of chemical pest management C-T , while the third treatment was mixed pest management M-T. Insect sampling was conducted using sweep net, pitfall trap, and direct observation for 10 weeks after planting. Overall, it was found morphospecies, 9 Orders, 56 families, with a total abundance of individuals per planting season. High insect diversity and abundance were found in the plots using low synthetic pesticides.
In recent years the field of entomology, due in part to the penetration of other disciplines, has made rapid progress. Not only is the book interesting and informative, but it provides useful, innovative research advances and will serve as a valuable resource for entomologists, zoologists, botanists and other researchers in the field of plant protection. Skip to main content Skip to table of contents. Advertisement Hide.
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Blogging about field adventures, interesting species, and wildlife ecology and conservation. Blog post by Christopher E. Smith FieldEcology. Subscribe via e-mail, RSS, or follow on Twitter. This blog post is an adaptation of a talk presented at the annual meeting of the M innesota Chapter of The Wildlife Society held in Mankato, Minnesota. The topic of insect conservation on lands managed via the use of prescribed fire is complex, and this is my attempt to briefly cover a few important aspects to consider.
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Request PDF | On May 1, , M. M. Gossner published Daly and Doyen's Introduction to Insect Biology and Diversity. 3rd edJames B.Reply
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The damaging effects of insects on cultivated plants could be broadly divided into two categories viz-viz Direct and Indirect.Reply