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Entomology :

the branch of zoology that studies insects. Also called insectology . The scientific study of insects. entomology - the branch of zoology that studies insects Entomology

Word History:

Scientists who study insects (there are close to a million that can be studied!) are called entomologists. Why are they not called "insectologists"? Well, in a way they are. Word History

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The word insect comes from the Latin word insectum , meaning "cut up or divided into segments." (The plural of insectum , namely insecta , is used by scientists as the name of the taxonomic class that insects belong to.)

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This Latin word was created in order to translate the Greek word for "insect," which is entomon . This Greek word also literally means "cut up or divided into segments," and it is the source of the word entomology.

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The Greeks had coined this term for insects because of the clear division of insect bodies into three segments, now called the head, thorax, and abdomen.

Characteristics of Insects :

General characteristics of all [most] insects. Bilateral symmetry, segmented [ metameric ] bodies. Advanced cephalization with an anterior brain and ventral nerve cord having segmental ganglia . Jointed appendages Characteristics of Insects

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Three body regions [ tagmata ]: head, thorax, and abdomen; Head: formed by tagmosis of primitive ancestral somites with segmental appendages modified to mouth-parts oral opening, or mouth one pair of sensory antenna compound eyes usually present, especially in adults simple eyes often present as well

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Thorax: composed of three body segments posterior to the head pro-, meso -, and meta-thoracic segments specialized for locomotion three pairs of legs, one or two pairs of wings [or wings absent] if present, wings are on the meso - and metathorax only

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Abdomen: simplest of insect tagmata 11 abdominal segments primitively, variously modified in modern insects genital openings usually on segments 8 and 9 anal opening usually on terminal segment no appendages on abdominal metameres

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Wings, if present, are not homologous with any vertebrate Chitinous exoskeleton: covers the entire body surface provides semipermeable barrier, especially important in limiting water loss anchors muscles provides joint articulations composed of hardened, sclerotized plates [ sclerites ] and flexible, membranous sections requires periodic molts to permit growth and development

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Stage-structured life-histories, usually delineated by molts . Open circulatory system; hemocoelomic body; organs bathed in hemolymph dorsal "heart" Ventral nerve cord; dorsal anterior ganglion; circumenteric connectives

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Tracheal system for gas exchange: few insects possess chemical O 2 carriers tracheal tubes ramify throughout the body to allow direct atmospheric gas exchange for most body cells

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Malphigian tubule system for nitrogenous waste disposal [contrast with metanephridia in annelids] system of tubules that filters the body fluid [ hemolymph ] and disposes of the filtrate via the alimentary canal functionally analogous to vertebrate kidneys

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