Insect morphology Wikipedia.Insectmorphology is the study and description of the physical form of insects.The terminology used to describe insects is similar to that used for other arthropods due to their shared evolutionary history.Three physical features separate insects from other arthropods they have a body divided into three regions head, thorax, and abdomen, have three pairs of legs, and mouthparts located outside of the head capsule.It is this position of the mouthparts which divides them from their closest relatives, the non insect hexapods, which includes Protura, Diplura, and Collembola.There is enormous variation in body structure amongst insect species.Individuals can range from 0.These modifications allow insects to occupy almost every ecological niche on the planet, except the deep ocean and the Antarctic.Titles A to Z Download PDF.STATRefs a la carte subscription model allows you to build a collection of titles to suit your specific needs.Browse the following list.Ferris Netter Advisor Desk Display Charts 1e Netter Clinical Science Document about Ferris Netter Advisor Desk Display Charts 1e Netter Clinical Science is available.This article describes the basic insect body and some of the major variations of the different body parts in the process it defines many of the technical terms used to describe insect bodies.Anatomy summaryeditInsects, like all arthropods, have no interior skeleton instead, they have an exoskeleton, a hard outer layer made mostly of chitin which protects and supports the body.The insect body is divided into three parts the head, thorax, and abdomen.The head is specialized for sensory input and food intake the thorax, which is the anchor point for the legs and wings if present, is specialized for locomotion and the abdomen for digestion, respiration, excretion, and reproduction.Although the general function of the three body regions is the same across all insect species, there are major differences in basic structure, with wings, legs, antennae, and mouthparts being highly variable from group to group.ExternaleditExoskeletoneditThe insect outer skeleton, the cuticle, is made up of two layers the epicuticle, which is a thin, waxy, water resistant outer layer and contains no chitin, and the layer under it called the procuticle.This is chitinous and much thicker than the epicuticle and has two layers, the outer is the exocuticle while the inner is the endocuticle.The tough and flexible endocuticle is built from numerous layers of fibrous chitin and proteins, criss crossing each other in a sandwich pattern, while the exocuticle is rigid and sclerotized.The exocuticle is greatly reduced in many soft bodied insects, especially the larval stages e.Fundamentals Of Anatomy And Physiology 7Th Edition Pdf' title='Fundamentals Of Anatomy And Physiology 7Th Edition Pdf' />Chemically, chitin is a long chain polymer of a N acetylglucosamine, a derivative of glucose.In its unmodified form, chitin is translucent, pliable, resilient and quite tough.In arthropods, however, it is often modified, becoming embedded in a hardened proteinaceous matrix, which forms much of the exoskeleton.In its pure form, it is leathery, but when encrusted in calcium carbonate, it becomes much harder.The difference between the unmodified and modified forms can be seen by comparing the body wall of a caterpillar unmodified to a beetle modified.From the embryonic stages itself, a layer of columnar or cuboidal epithelial cells gives rise to the external cuticle and an internal basement membrane.The majority of insect material is held in the endocuticle.The cuticle provides muscular support and acts as a protective shield as the insect develops.However, since it cannot grow, the external sclerotised part of the cuticle is periodically shed in a process called moulting.As the time for moulting approaches, most of the exocuticle material is reabsorbed. 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In moulting, first the old cuticle separates from the epidermis apolysis.Enzymatic moulting fluid is released between the old cuticle and epidermis, which separates the exocuticle by digesting the endocuticle and sequestering its material for the new cuticle.When the new cuticle has formed sufficiently, the epicuticle and reduced exocuticle are shed in ecdysis.The four principal regions of an insect body segment are tergum or dorsal, sternum or ventral and the two pleura or laterals.Hardened plates in the exoskeleton are called sclerites, which are subdivisions of the major regions tergites, sternites and pleurites, for the respective regions tergum, sternum, and pleuron.Head of Orthoptera, Acrididae.Larva of beetle, family Cerambycidae, showing sclerotised epicranium rest of body hardly sclerotised.Larva of Syrphid fly, member of Cyclorrhapha, without epicranium, almost without sclerotisation apart from its jaws.The head in most insects is enclosed in a hard, heavily sclerotized, exoskeletal head capsule, or epicranium.The main exception is in those species whose larvae are not fully sclerotised, mainly some holometabola but even most unsclerotised or weakly sclerotised larvae tend to have well sclerotised epicrania, for example the larvae of Coleoptera and Hymenoptera.The larvae of Cyclorrhapha however, tend to have hardly any head capsule at all.The epicranium bears most of the main sensory organs, including the antennae, ocelli, and the compound eyes.It also bears the mouthparts.In the adult insect the head capsule is apparently unsegmented, though embryological studies show it to consist of six segments that bear the paired head appendages, including the mouthparts, each pair on a specific segment.Each such pair occupies one segment, though not all segments in modern insects bear any visible appendages.Of all the insect orders, Orthoptera most conveniently display the greatest variety of features found in the heads of insects, including the sutures and sclerites.Here, the vertex, or the apex dorsal region, is situated between the compound eyes for insects with hypognathous and opisthognathous heads.In prognathous insects, the vertex is not found between the compound eyes, but rather, where the ocelli are normally found.This is because the primary axis of the head is rotated 9.In some species, this region is modified and assumes a different name.The ecdysial suture is made of the coronal, frontal, and epicranial sutures plus the ecdysial and cleavage lines, which vary among different species of insects.The ecdysial suture is longitudinally placed on the vertex and separates the epicranial halves of the head to the left and right sides.Depending on the insect, the suture may come in different shapes like either a Y, U, or V.Those diverging lines that make up the ecdysial suture are called the frontal or frontogenal sutures.Not all species of insects have frontal sutures, but in those that do, the sutures split open during ecdysis, which helps provide an opening for the new instar to emerge from the integument.The frons is that part of the head capsule that lies ventrad or anteriad of the vertex.The frons varies in size relative to the insect, and in many species the definition of its borders is arbitrary, even in some insect taxa that have well defined head capsules.In most species, though, the frons is bordered at its anterior by the frontoclypeal or epistomal sulcus above the clypeus.Laterally it is limited by the fronto genal sulcus, if present, and the boundary with the vertex, by the ecdysial cleavage line, if it is visible.If there is a median ocellus, it generally is on the frons, though in some insects such as many Hymenoptera, all three ocelli appear on the vertex.A more formal definition is that it is the sclerite from which the pharyngeal dilator muscles arise, but in many contexts that too, is not helpful.In the anatomy of some taxa, such as many Cicadomorpha, the front of the head is fairly clearly distinguished and tends to be broad and sub vertical that median area commonly is taken to be the frons.The clypeus is a sclerite between the face and labrum, which is dorsally separated from the frons by the frontoclypeal suture in primitive insects.The clypeogenal suture laterally demarcates the clypeus, with the clypeus ventrally separated from the labrum by the clypeolabral suture.The clypeus differs in shape and size, such as species of Lepidoptera with a large clypeus with elongated mouthparts.The cheek or gena forms the sclerotized area on each side of the head below the compound eyes extending to the gular suture.Like many of the other parts making up the insects head, the gena varies among species, with its boundaries difficult to establish.For example, in dragonflies and damselflies, it is between the compound eyes, clypeus, and mouthparts.
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