Insects or entomological (scientific name Insecta Linnaeus, 1758), are a class of living belonging to the large phylum Arthropoda. This class represents the largest groups of animals that inhabit the Earth, numbering over one million species, equal to five sixths of the entire animal kingdom. Are believed to be among the oldest settlers of the land as fossil insects discovered date from the Devonian. The heterogeneity in morphology, in the anatomy, biology and nell'etologia conferred to insects, more than 300 million years, a major role in the colonization of the Earth, in any environment where there is organic matter, with demonstrations a remarkable capacity for competition. The insects, therefore, are organisms that, in positive or negative, have a close relationship with the man and his activities, to influence, more or less directly, economics, nutrition, habits and health. General characteristics The shape, size and general appearance of the body are of extreme variability in size Tricogrammatidi many Hymenoptera order of two tenths of a millimeter and, however, rarely exceed one millimeter in length. On the contrary, the body of Hercules Beetle Scarabeide Dynastes can reach 17 cm in length and Saturnide Attacus atlas moth, considered the largest butterfly in the world, has a wingspan of over 25 cm. The shapes vary widely, also including those of the convoluted Rincoti coccidia, and may disappear altogether and morphological differentiation of regions of the appendages of the body, except the apparatus jug.
Exoskeleton: The support and the attachment of muscles, in arthropods, is provided by an external skeleton that also serves as the seed coat. The exoskeleton is composed of several layers, organized in a basement membrane, a simple epithelium (epidermis) and a passive layer, rigid and stratified (cuticle). From it are derived the main properties exoskeleton, its composition part organic macromolecules that confer rigidity, strength, water resistance, elasticity and flexibility. The thickness of the cuticle is not uniform, but is interrupted at the joints, replaced by a membranous tissue, and suturing. These are lines of least resistance, which separate the portions of the exoskeleton itself (sclera). Membranous areas provide the flexibility and movement, the sutures give less resistance which allows the unfolding of the suit. The surface of the exoskeleton is often full of hair, bristles, scales and sculptures, sometimes essential for taxonomic.
The head is the region composed of the first six somites that come together in a structure where you lose the original metamerism. The first three somites form the procefalo, the next three gnatocefalo him. The exoskeleton forms a capsule which has two openings, the peristome and the foramen magnum. The first marks the mouth opening, the second connects the head to the chest.
Cape : External cephalic structures have two predominant functions: the perception of sensory stimuli and the first supply phase (socket, processing and food ingestion). These facilities generally include a pair of antennae, two compound eyes, 2 or 3 ocelli, and finally, the appendices apparatus jug. The antennae are organs with predominantly sensory function, and development of various forms, consisting of a variable number of items, such antennomeres, more or less differentiated. The compound eyes are complex structures delegated to visual perception, formed by the aggregation of elementary units called ommatidia. The eyes are rudimentary ocelli absent in some taxonomic groups, which are essential for perception of orientation in flying insects. Commitment are the appendices which are articulated to the peristome. Are represented in dorso-ventral, one pair of mandibles, a pair of jaw and lower lip (labium). The front of the mouth opening is bounded by the upper lip (labrum) while helping to form the mouthparts, is actually derived from the first somite of procefalo. The oral cavity, bounded by the mouthparts, is divided into two parts, a dorsal and ventral from prefaringe. On the jaw and lower lip are part of the general palps, organs pluriarticolati deputies to the perception of sensory stimuli. The typical example is chewing mouthparts, adapted the taking of solid food and their shredding. Many groups have, however, systematic changes in anatomical, morphological and functional features that are easily adapted to other functions. This is known as piercing-sucking apparatus, sucking, lapping-sucking.
Chest: it derives from the combination of three somites and is primarily home to the motor organs. It is divided into pro-, meso-and metathorax. The exoskeleton of each segment is attributable to a ring formed by the organization of four areas: a backbone, called back, or known tergite, two sides, called the pleura, a ventral, or Stern Stern said. In the terminology is used to specify both the thoracic segment and the area to which reference is made: for example, the tergites of the three segments are referred to as pronotum, mesonotum, metanotum; similar names are used to indicate the sternum, the pleura and, often, individual sclerites and appendages. The morphology of the tergite, pleura and sternum can be relatively simple or complicated by the presence of suture lines, particularly in the second and third segment of the winged forms. Marked differences also exist in the development of its three segments: the apterous forms have a relatively well-developed prothorax and a substantial homogeneity of the three segments, the prothorax winged forms have a rather poorly developed and the other thoracic segments are highly developed in relation to the role played by their wings. The more complex structures are found in flies, in which the mesothorax has a predominant development than the other segments, and in Apocrita Hymenoptera, where the establishment of the chest is also involved in a part of The urite, forming the fourth thoracic segment (propodeum). In the generality of Insects is a pair of legs for each thoracic segment, which may secondarily reduced or absent. The presence of three pairs of thoracic legs usually is detected even in juveniles. In some larvae are present abdominal organs of locomotion (pseudozampe), but in others may be atrophic or absent. Appendages are free and pluriarticolate, consisting of coxa (or hip), trochanter, femur, tarsus, pretarso and nails. The tarsus is in turn divided into several articles and those tarsomeri pretarso tarsomero past is hidden. Pretarso are divided on the nails, which allow adhesion to rough surfaces, and other organs with specific forms and functions. The primary function of the legs is that locomotion, in which case the legs are called slider or outpatient. Morphological and anatomical adaptations are often aimed at functions such as swimming, predation, digging, jumping.
The wings are present in the adult stage and as a primary character, in all insects except Apterygota. It is frequently meiotterismo secondary, progressive reduction of the wings until the complete disappearance (wingless). They are worn by the mesothorax and metathorax. Lateral expansions are morphologically exoskeleton of the thorax and structurally consist of two overlapping sheets: a ridge, in continuity with the tergite, a ventral, continuous with the pleura. In most insects the continuity is interrupted by a system composed of three joints and two sclerites pterali differentiated from pleural thoracic sclerites. The wings of insects have no intrinsic muscles and the movement has spread to the action of muscles in the chest. The wing is traversed by piping, these ribs or veins, which is on the haemolymph, nerve and trachea. The course of the ribs is an important element in determining in some taxonomic orders. The wing morphology varies greatly according to the systematic group. In general they are membranous, sometimes more or less sclerificate. The front often have a greater development and there may be specific linkages for synchronizing the movement. The wing area is divided into three regions, respectively called Feather, anal and Jugal: the first has the greatest development and enhanced robustness. The primary function is that of the flight, however, the adjustments would affect this function until it is lost altogether in favor of other goals, turning the wings in the organs of protection, regulation of, etc..
Abdomen: is the region in which morphological reproductive organs are located. Consistency more delicate than the thorax, is composed of 11 segments, such uriti but urite XI [9] is atrophic or rudimentary. In more advanced systematic groups, however, the number of uriti tends to decline for the last modification or involution. Urite Each has a shape of a ring due to the one in which there are four areas: a dorsal (urotergo), a ventral (urosterno) and two lateral membranous, sometimes sclerificate for expansion of the dorsal or ventral sclerite. The uriti are divided between them by the intersegmental membrane, a structure supple and flexible, allowing the expansion of the region and some mobility. Abdominal appendages are usually not very noticeable in comparison with thoracic and cephalic. In most insects are the genitalia (genital gonapofisi or armor) is present in male copulatory organ, formed by expansion of the ninth urosterno, and females the ovipositor, formed by expansion of the VIII and IX urosterno. The ovipositor can reach a remarkable development in some taxonomic groups, sometimes turns into a sting and becomes an instrument of aggression and defense, in others it may be entirely absent and the function is performed by other structures which take the name of ovipositor replacement. Other appendices Insects are common in many circles, placed on either side of the last urite. Rudimentary or absent orders less advanced in some taxonomic groups can achieve a remarkable development. The larvae are often present processes that perform various functions. The most common are the larvae pseudozampe eruciformi
Anatomy : Cerebro - ganglion ipocerebrale - allatum Body - Body throat - Aorta - ganglion stomach -
craw - gizzard, heart valve - mesentery - ; Emocele - ventricular - Heart - ostiolo - Rectum - Anus - Vagina - frontal ganglion - Track periesophageal - Epifaringe - Pharynx - Gnatocerebro - Esophagus - ventral ganglia - Pyloric valve - Malpighian tubes - Proctodeo - Ovariolo - Ovary - spermatheca
Compared to vertebrates, insects and arthropods invert the placement of the axles systems: the circulatory system and peripheral nervous system, respectively, assume a dorsal position and ventral, while the digestive tract is located in a central position. While maintaining some similarities, the anatomical structure differs markedly from that of vertebrates but often you tend to borrow for relevance, terminology specific organs and systems.
endoskeleton : The inner exoskeleton endoskeleton is an extension that favors the attack muscle and supporting bodies. It consists of a set of internal processes, and development of various forms. The head is located the tentorium, the more training, present in almost all the insects. Rules the brain and the esophagus and it is connecting the antennas and the extrinsic muscles of the buccal apparatus. In the chest are present, for each segment, a pair of Fragma (back), one of apodemi (side) and Furche (Learn and ventral). Abdomen, finally, are reduced to apodemi dorsal and ventral development.
muscular system: muscles of insects are almost all type of striated stick to the cuticle or exoskeleton for dell'endoscheletro fibrils by non-contractile (tonofibrille), comparable to the tendons of vertebrates. Their number is high, the order of thousands [10]. They differ in skeletal and visceral: the former have names derived from their location or their function and are generally equal and symmetrical. They are responsible for the movement of appendages and morphological regions of the body, so they are also known as somatic. The visceral musculature is associated with internal organs and is only partly made up of smooth muscle fibers.
The digestive system of insects is a pipe that starts from the opening mouth and ends in the anal. It is divided into three distinct components: stomodeo, the mesentery, the proctodeo, respectively, also known as intestine anterior, middle and rear. The path may be more or less according to tortuous anatomical and physiological complexity of the species. In more primitive forms is a longitudinal channel that runs through the whole body, while specific skills are the cause of structural complications. Through the three morphological regions available over the ventral ganglionic chain and under the dorsal vessel. The terminology used to distinguish the different sections is often borrowed from that of vertebrates, but the profound structural and physiological differences do not imply any homology. The stomodeo performs the functions of ingestion and before food preparation and, in some insects, the temporary storage. Part of opening mouth and ends at the heart valve which flows into the mesentery. Process in the cephalo-caudal, is divided into the following sections: oral cavity, pharynx, esophagus, gizzard, the latter developed mainly in insects with chewing mouth parts. The stomodeo sometimes presents a diverticulum, the craw, which can reach large enough to occupy even the abdomen. The functions have dell'ingluvie justify such special designations (eg bag supers in Bees, Ants in the social stomach bag of blood in mosquitoes). The mesentery is the site where digestion takes place itself, with the demolition of the enzyme macromolecules and the absorption of nutrients. The food bolus is enveloped by a membrane (membrane hyphae) produced by epithelial cells of the mesentery and forming a vesicle inside which carry out the demolition process. The same membrane filter acts as a dialysate, preventing direct contact of the bolus and digestive enzymes into the wall of the mesentery. The proctodeo is back and is Member of primarily the reabsorption of water and the elimination of the non-digested and catabolites. In the initial section is related to the excretory system, as there confluence of the Malpighian tubes. It begins at the pyloric valve, but in some taxonomic groups the mesentery and the dead-end and therefore break the continuity of the digestive tract. In the anteroposterior direction, the proctodeo is divided into sections that have names borrowed from the digestive tract of vertebrates, the order stands the ileum, colon, rectum. The nature of the histological and stomodeo proctodeo is ectodermal, the mesentery is probably entodermica. The walls of stomodeo proctodeo and are made from the inside to the outside by a cuticle layer, called intimate by an epithelium, a basement membrane, by a muscular tunic consists of a bundle of inner and outer longitudinal muscles of circular muscles and, finally, a peritoneal tunic of connective tissue. The muscular tunic includes stomodeo in an internal beam of longitudinal muscles and an outer circular muscles. Proctodeo in the muscle bundles are three: an intermediate longitudinal muscles between two layers of circular fibers. The mesentery, proceeding from the inside out, consists of the membrane hyphae, a simple epithelium composed of cells that have different development, a basement membrane, a muscular coat consisting of a bundle of internal circular muscles and an outer longitudinal muscles and, finally, the intestinal tunica. The model structure of the digestive tract can undergo profound changes according to the taxonomic groups. One of the most significant is the presence of the filter chamber in almost all Rincoti Omotteri. This organ has functions of dialysis and bypass: To avoid excessive dilution of digestive juices of the mesentery, the filter chamber separates a substantial portion of the liquid and sugar from protein and lipid macromolecules. The first phase is diverted in proctodeo, while the macromolecules will follow the normal path, entering the mesentery. This adaptation is its honeydew-producing insects, excrement liquid high sugar content, of great ecological importance.
Respiratory : the transport of oxygen to the cells are not entrusted to the bloodstream, so the insects are marked differences from the circulatory and respiratory systems of vertebrates. The respiratory Insect takes part in the metameric structure of their body, but inside is resolved in a complex network of tubes that carry oxygen to the cells. Stigmas forming apparatus, the tracheae and tracheole. The stigmas or tracheal spiracles are openings, the number of 10-10 pairs, on either side of one or more thoracic and abdominal segments. The tracheae tubules are derived from intussusception of the integument, which retain the same structure. There are three branches from each tracheal stigma linked together and with those of adjacent segments, forming a complex network anastomosed. The tracheae branch in tracheole in turn, of a size smaller, which form a network of transportation. The most tracheole have small diameter of the order of several microns. In many insects the tracheae can expand to form the air sacs, whose function is to build up reserves of air or act as a hydrostatic or aerostatic bodies.
The circulatory system is open-ended: the humoral no movement takes place inside pots, but in a cavity, called emocele lacunoma or in contact with organs and tissues in all parts of the body including the ribs of the wings. Only partially takes place in a vase, which has the functions of a heart. The humor that flows nell'emocele, the hemolymph, performs both functions of the lymph and blood of vertebrates, except the transport of oxygen, Insects that are entrusted in the respiratory tract [14]. The hemolymph was instead charged with transporting nutrients and catabolites and the immune system. The emocele is divided by two baffles into three longitudinal cavities interconnected. Formed by connective tissue and muscle, have a peristaltic movement which promotes circulation to the caudal area and the entrance at the rear of the vessel back button. The dorsal vessel differs in two sections, one in the rear (heart) and a front (aorta). The heart is divided into connecting rooms (ventricles), each with two valves (ostiolo) governing the continuity with the emocele. The muscular system associated with the dorsal vessel gives the pulse that push the blood to the cephalic region. Other accessory organs buttons are located in the Appendices and promote circulation in organs that would offer greater durability. The hemolymph of insects differs substantially from the blood of vertebrates, is composed of a liquid part (plasma) and a mobile phone, made by haemocytes. Any pigments, usually yellow or green, have respiratory functions.
Nervous System: protocerebrum - deutocerebro - tritocerebro - gnatocerebro - ventral ganglionic chain. In analogy with the nervous system of vertebrates, insects stands a central system, a peripheral and a visceral, the latter with neurovegetative functions. The neurons are of three types: sensory, motor and associative. The former are associated with sensory receptors, are bipolar and transmit impulses from the periphery to the ganglia. The latter have the body located in the basal ganglia are unipolar and send impulses to the muscular system. The third, also located in the basal ganglia are multipolar and assuming functions of association. The transmission of signals follows the same mechanisms of Vertebrates: along axons in the form of electrical impulse, to alteration of membrane potential, and synapses with the release of a chemical messenger, acetylcholine. Many insecticides, acting as inhibitors of acetylcholinesterase, also have neurotoxic effects on vertebrates. The central nervous system has an organization metameric: it consists of a double chain of ganglia, which is located in ventral position in the digestive tract, with a pair of ganglia for each segment. The ganglia are connected by transverse and longitudinal nerve fibers, which disappear with the possible merger. The metameric structure disappears at the beginning, with the fusion of the cephalic ganglion in two masses. The first, the brain, brain or ganglion sopraesofageo, is located above the stomodeo. The second, called gnatocerebro sottoesofageo or ganglion, is located under the stomodeo. The two connessure that connect the brain with the gnatocerebro form a ring (or track parastomodeale periesophageal) through the esophagus. The two masses ganglion innervate organs and the appendages of the head. Depart from the brain, in addition, the dorsal sympathetic and cardio-aortic neuroendocrine system. The visceral nervous system is complex and autonomic apparatus maintains its own autonomy from the central, while there are related. It shall be responsible for the innervation of internal organs and is composed of three distinct systems: the sympathetic or dorsal stomatogastrico, the sympathetic ventral, and caudal sympathetic. First, learn, is localized in the brain and in the dorsal part of stomodeo to enumerate the initial part of the digestive system. The second part of the chain of ventral ganglia and innervate the trachea and the stigmas. And the third, part the last couple of chain and innervate the ventral proctodeo and genital organs. The peripheral nervous system includes the axons of motor neurons, which innervate the striated muscles, and neurons associated with sensory receptors. It grows in all parts of the body and is associated with the ganglia of the central nervous system. The excretory apparatus
ensure the elimination of waste products (catabolites). It consists of localized organs (Malpighian tubes) and common (or nefrociti nephritis). In addition there are other tissues and organs that perform excretory functions also secondary. The Malpighian tubes are made of kidney tubules, thin, dead-end, which are included in proctodeo, immediately after the pyloric valve. Absent in aphids, other insects are present their number varies from a few to over 200. Nell'emocele float or adhere to proctodeo. The function is to filter the products of protein metabolism (ammonia, urea, uric acid) and adjust the balance of salt, removing waste substances dall'emolinfa. Second symbiotic microorganisms can accommodate, producing silk, glues substances, etc.. The nephritis are scattered groups of cells, sometimes isolated, associated with stomodeo, salivary gland and dorsal vessel. Their function is to regulate the pH and act as excretory organs dell'emolinfa intermediate catabolites turning in forms that are then eliminated by the Malpighian tubes.
secretory apparatus: Insects have glandular apparatus of a complex, divided into the exocrine system, consisting of external secretion glands, and in an endocrine gland composed of internal secretion. The endocrine system is made up of cells and organs that have relation with the nervous system. Regulates the biology of the insect and reaches high levels of organizational complexity comparable to that of higher animals. A special feature that distinguishes vertebrates from insects is the lack of features in the appearance of endocrine secretion player. The endocrine glands of vital importance are identified in four structures: the endocrine system of the brain, heart, and beside the bodies and glands prothorax. The primary function performed by these glands is the regulation of postembryonic development, but individually these structures also control other biological processes. The endocrine system consists of brain nerve cells of the brain that have lost the ability to transmit nerve impulses becoming neuroendocrine glands. The main activity consists in the juvenile stage, with the production of the brain, transported by axons to cardiac bodies. They accumulate the hormone, modify it and put it in a circle nell'emolinfa. Secondary functions of the bodies consist of the cardiac release of hormones that regulate the functioning of certain organs and the muscular system. The bodies are beside themselves gentlemen, behind brain hormone stimulation, production of neotenina responsible for the persistence of juvenile characters. The glands are located ventral prothorax, usually between the head and chest. Their primary function is to release the hormone upon stimulation of the brain, dell'ecdisone, which leads the pack. The system is composed of exocrine glands uni-or multicellular. The latter are themselves simple or complex, the first with a single excretory duct common to all cells, the other with an excretory duct confluence for each cell a common tank. Other classifications could include the location and distribution in the body. With regard to the nature of the secretion in the class there is a wide variety of glands, many of which are, however, specific to one or more taxonomic groups. Glands that perform the same function may also vary by location, structure and function in development of various systematic categories. A discussion of the anatomy and physiology of the exocrine system can not be separated by a reductive simplification, given the extreme heterogeneity. For further information please refer to the individual groups so systematic.
Among the glandular systems of most frequently are cited as follows:
accessory glands of the genital tract. Present in both sexes, secrete substances that are usually carriers of reproduction: the secret of the males has trophic functions in respect of the sperm, that of females involved, in general, the dynamics dell'ovideposizione. There is no lack specific functions unrelated to reproduction (eg, the venom glands of Hymenoptera aculeata).
pheromone glands. Present in various orders and generally localized in the abdomen secrete volatile substances active at low concentrations, usually perceived only by individuals of the same species. Pheromones are mostly a function of chemical communication in relational life and are involved in reproduction, in co-operation within communities, in the dynamics of intraspecific competition.
ceripare glands. Common among the Hymenoptera, the Rincoti Omotteri and some beetles are in generally widespread in the integument and secrete the wax. The secret is used for various purposes, including to protect the body is common.
scent glands. Usually present in the dorsal part of the body, are found in various orders (Rincoti, Coleoptera, Diptera, Hymenoptera, Lepidoptera, Neuroptera). The secret is composed of volatile substances that can have a repulsive effect or, conversely, attractive. In the first case was for defensive purposes, in the second often leads to the establishment of a symbiotic relationship.
salivary glands. In the cephalic region of the generality of Insects, are associated with the mouthparts. Emit digestive juices often contain substances with specific action in certain contexts (anticoagulants, declorofillizzanti, etc.).
sericipare glands. Present in many orders, show a remarkable variety in the location and structure. Secrete the silk used, as appropriate, for the construction of cocoons, nests, ooteche, protective capsule of the body, etc..
reproductive system: insects, hermaphroditism was found only in Icerya purchasi and in some Diptera, so the reproductive system differs in two distinct sexes from embryonic homologous structures. The gonads of mesodermal origin, are the site of development of gametogenesis. They differ in the testes (male) and in ovaries (female) and are composed of tubular elements (ovarioli and testes) in confluent gonodotti equal, in both sexes of gametogenesis stages follow each other along the distal-proximal tubule in order. Gonad follow gonodotti Similarly, ducts ectodermal origin that converge into a common gonodotto, you learn. The gonodotto common in the male ejaculatory duct and is said to maintain the appearance of an excretory duct that communicates with the copulatory organ. In the female differs in the vagina and usually communicates with the ovipositor, and in some taxonomic groups may have a diverticulum with independent opening, the bag copula, used for the copula. Another body is the differential in the female spermatheca, a vesicle in dead-end connected to the vagina, in which sperm are maintained in the range of time between mating and fertilization. In both sexes, the apparatus has accessory glands, which discharge secreted into the proximal common gonodotto. The secretions have different functions, according to the sexes and species, and different types can coexist in the same individual glandular. The secretion of the male gender plays in the function of lubricating and nourishing sperm. In the female nature and function of the secreted mainly depend on the glandular type. The most common are those colleteriche glands and their secretion is used as an adjuvant dell'ovideposizione like glue Eggs, for the construction of ooteche, etc.. Other glands, such spermofile, secrete a nutritive fluid for sperm stored in spermatheca. In Apocrita Hymenoptera venom glands are also present: their secretion, issued by the ovipositor or sting, has an associated action or oviposition integrates the function of secondary means of offense and defense in the female sterile. The external genitalia are different in general as a process of forming urosterni genital armor, an important element in determining taxonomic. In the male is differentiated from urosterno IX and forms the copulatory organ or edeago, used for mating. The edeago may lack in primitive insects: in this case the spermatozoa are released outside the capsule, called spermatophores, which are then picked and introduced by the female. In the female, the genital armature, ovipositor that is differentiated from urosterni VIII and IX, and is generally composed of three pairs of valves, sometimes exceptionally long. It is used as a body to lay their eggs and can pierce plant tissues or animals. In many insects, the ovipositor may be missing entirely or is functionally replaced by the last uriti adjustments, which are called ovipositor replacement. The ovipositor in Hymenoptera Aculeate undergoes anatomical and functional adaptation that turns it into an instrument of offense and defense; in this case is called a sting or a sting.
Reproduction is typically by sexual contact (anfigonia), with the coupling between separate sexes and fertilization of eggs by sperm. The mechanisms that regulate the anfigonia vary from species to species and, sometimes, have levels of complexity that affect the dynamics of an entire community (social insects). All'anfigonia accompany other forms of sexual reproduction, which often have an impact on population dynamics and, in some species, sexual reproduction prevails. In these cases, often used parthenogenesis, found in almost all the orders in various forms. A special case of parthenogenesis is pedogenesis, found in some Diptera and Coleoptera Cecidomiidi Micromalthus debilis: the larva brings to fruition the ovaries and generate like-minded individuals that develop at his own expense, killing her. Another type of sexual reproduction is the polyembryony, which is the source of an indefinite number of larvae from the segmentation of a single egg, found in some Hymenoptera Terebranti. Sex determination does not follow a unique pattern. In the generality of the species, sex is determined by the presence of a sex chromosome X in a double dose of sex and single dose, or combined with a Y chromosome in the opposite sex. Eterogametico sex is male, except for Lepidoptera and Trichoptera. In some orders sex is instead determined by the ratio between anfigonia and haploid parthenogenesis: females originate from fertilization, parthenogenesis by males. The majority of insects are oviparous, but there are also viviparity and ovoviviparous. These different behaviors can coexist even within a single species or even the same individual.
postembryonic development is based on the metamorphosis of insects, discontinuous sequence of physical changes that, starting from the egg, leading to the formation of the adult. In Insects and, more generally, in arthropods, we must distinguish between the weight gain (weight gain), which proceeds continuously, from much linear (increase in size), which is rather discontinuous. Because of the rigid exoskeleton, the weight gain in a young insect is not accompanied by an increase in size: at some point, the old cuticle (Exuvia) tears and the individual comes out with a new, able to contain the increase in size. This phenomenon is called moulting. The suit may also be accompanied by the metamorphosis, which is a physical transformation that is not limited only to the increase in size. Growth and metamorphosis are regulated by neurohormonal mechanisms can be summarized in the interaction between two hormones, ecdysone and neotenina. The ecdysone stimulates the genesis of the new cuticle, so it is the biological signal that initiates a new suit. The neotenina, however, inhibit the emergence of the adult characters, which remain latent in the form of sketches. The ecdysone stimulates moulting and metamorphosis, but in the presence of neotenina the metamorphosis is inhibited. The classification of types of metamorphosis relates to schemes for which there is no uniformity of approach between the authors. Stages of ontogenetic development can be construed in different aspects and terminology used is not always so clear. For further information please refer to the details described in the item analysis. At first glance, there are two basic types of metamorphosis, marked with the words of complete and incomplete metamorphosis. The morphological element that distinguishes the two types is how they are formed, where appropriate, sketches wing.
In complete metamorphosis, which is identified with the holometabolous, the juvenile stage is said to differ greatly from the adult and larva (also known as image). This difference is the basis for profound changes, which are carried out during the Pupation, pupal stage, often preceded by a brief phase (eopupa): an insect undergoes a drastic reconstruction of the morphological and anatomical structure, with the exception of the nervous system and circulatory system. The magnitude of the changes is such that, at this stage, the state of immobility of the insect. The sketches are internal wing and appear only in the pupa stage. This kind of metamorphosis of insects is their most advanced, winged or secondarily wingless, whose orders are included in the cohort of Endopterigoti. In more primitive forms of complete metamorphosis, the pupa is mobile. In fact, the pupa is a mobile adult phase farata, stage of transition, following the last changes, during which the adult, although fully formed, has not yet abandoned the Exuvia. In incomplete metamorphosis, which is identified with the heterometabolous just Insects winged or secondarily wingless, less advanced, the cohort of Esopterigoti. The juvenile stage is called nymphs and differs from the adult only for minors size, lack of sexual characteristics and, in the winged forms, the absence of wings. The transition from juvenile to adult stage takes place in one or more stages of the nymph, which occurs during the onset of external wing buds. The nymph is floating except neometabolia, a type of metamorphosis heterometabolous intermediate between itself and the holometabolous. The two described above is a third type, called ametabolic, when, in reality, there is no metamorphosis. The ametabolic occurs in primitive wingless insects (Tisanuri): in this case, the juveniles do not show any morphological difference compared to adults, if not in size, and development takes place with mute with no metamorphosis. The ametabolic pseudoametabolia not to be confused with a form of heterometabolous typical species secondarily wingless. The scheme described is complicated when one considers the metamorphosis neometabolia a distinct and intermediate between incomplete and complete and that if we take into consideration the variations that occur within and dell'eterometabolia dell'olometabolia. Finally, it distinguishes a fifth type of metamorphosis, catametabolia said, he sees a regression insect anatomy and morphology during ontogenetic development. In other words, the adult has a form and a simpler structure than that of juveniles. The catametabolia is actually a variant of the species due to adaptation to a especially ethology and is reflected by both nell'olometabolia is nell'eterometabolia.
Power: The majority of insect trophic relationships with the plants or animals, or clear a greedy scheme. They are also frequent scavenging or, more generally scavengers, there are finally cases of insects micetofagi. A strict classification, however, is not possible because the boundaries that define the diets are often blurred. Among the insects that feed on plants at the expense of living there are two categories: pests and fitomizi. They are often described, wrongly, as parasites, but the trophic relationship that binds them to the plants is identified with a form of predation due all'erbivoria. Reports can be more or less specific and species are distinguished monofaghe, oligofaghe and polyphagia. The pests have chewing mouth parts and erode the plant tissue by attacking the organs from the outside or from inside (the miners). An informal terminology identifies pests by organ or tissue attached: the fillofagi (at the expense of the leaves), the antofagi (flowers), the carpofagi (fruit), the xylophagous (wood), etc.. The fitomizi are insect mouthparts for piercing-sucking and feed at the expense of the juices or sap prepared epidermal cell phones. A particular group is represented by insects knot, which develop within histological alteration of the affected organ (gall). In this case the pest is best approached with the concept of parasitism. Regarding the zoofagia, you can make a distinction for the different area of \u200b\u200binterest, including species that attack and other vertebrates that feed at the expense of Invertebrates. Again you can find forms of monofagia, oligofagia and polyphagia. The first category includes a limited number of species, often medical or veterinary interest. The trophic relationships are situated halfway between parasitism and predation, with varying degrees of affinity to the first or second. They feed at the expense of the epidermis or its appendages or blood (blood-sucking parasites). There are few cases of predation itself (eg the Ditiscidi Rincoti Heteroptera and some also prey on small aquatic vertebrates). The shapes are generally similar to parasites epizootic, however, there are cases of endoparasites (eg, some families of Diptera). Among the carnivorous species also include purely scavengers who feed at the expense of the remains of dead vertebrates (sarcophagus). Most species, however, has a scheme zoofago trophic relationships with other arthropods and, in particular, with other insects. In these cases the relationships are identified with the real predation or the parasitoid, while cases of parasitism itself are quite rare. Among artropofagi also include oofagi that prey or parasitized eggs. In general, there are species of great interest because they can be exploited for biological control and integrated. Cannibalism is not uncommon, usually between predators but sometimes even among the pests, and this phenomenon occurs frequently in low food availability or in captivity. Less frequent is instead between individuals of the same parasitoid species, a phenomenon known by the term autoparassitismo and is found primarily in Afelinidi Hymenoptera, which are found in the behavior of natural interest, and in the above-mentioned species with pedogenic reproduction.
A special diet is that of glicifagi. These insects feed at the expense of sugars and in general use as a substrate to feed the flower nectar and honeydew emitted by Rincoti or juices leaking from wounds. The protein sources used are represented, as appropriate, pollen, animal droppings or from other materials. The mouthparts are kind of sucking or lapping or sucking-type chewing more or less adapted. Many glicifagi are important pollinators such as insects, as in the carriage of pollen, and thus promote cross-pollination. Some diets are complex and do not have a place well-defined: for example, some knot Hymenoptera parasitoids of insects can become pests when, once the victim, complete the their development cycle at the expense of feeding on the gall tissue. Even among the insects include, however, omnivore, able to eat foods with either source of vegetable and animal.
Ethology : One of the most interesting aspects of ethology is the life of social insects, species that have developed a complex level of gregariousness and organized caste based on building complex nests, the transmission of sensory stimuli, the care of children , research, procurement and storage of food, the regulation of reproduction, etc.. These ethological phenomena, taken together, determine the ecological success of the community by sacrificing the individual individual. The best known examples of social interaction, affecting mostly the Isotteri and Hymenoptera, plus a wide range of phenomena of social aggregation, represented in the most orders, with different levels of complexity with regard to internal relationships. Intraspecific aggregation are often associated with interspecific relationships within the ranks of the phenomena of symbiosis and commensalism. Apart from the social groupings, ethology of insects show interesting and varied behaviors regarding food, building nests, reproduction, migration, communication between individuals of the same species, the relationship with organisms of different species, the locomotion, camouflage, defense, the emission of light or sound, etc.. For a discussion of these issues may be found in entries for individual taxonomic groups.
population dynamics: the odd Bombich causes extensive defoliation during his grades cicliche.Anche with regard to population dynamics, occurring on different models, on which often interferes Man simplifying or altering ecosystems. In general, the insects - like most of the Invertebrates - a strategy based on the potential reproductive life (r strategy), because it shows an extraordinary rapidity of colonization of ecosystems to lose their equilibrium. This problem arises especially in the agro-systems, in which the loss of biodiversity creates imbalances that benefit their own species with large reproductive potential.
Under natural conditions, many species are based on changes in the dynamics: the population level is maintained for periods shorter or longer, in a lag phase, in equilibrium with the food availability and cenosis antagonists. Periodically, at more or less regular gradations occur, sudden changes in population density than the lag phase. During a grade will have three phases:
progradation: the population growth rate shows exponential under high biotic potential, the availability of nutritional resources and the low incidence of natural factors control;
climax: the population increases with decreasing increments until it reaches a maximum, at which stage they become the controlling factors of natural teeth population: intraspecific competition, reduced fertility, disease and population growth of the antagonists;
retrogradation : Due to the high incidence of natural control factors, mortality increases significantly and the population collapses more or less rapidly to printed on the equilibrium values \u200b\u200bof the lag phase. The phenomenon of gradation is found in forest ecosystems in general and particularly interested in the Lepidoptera and Coleoptera defoliators. The amount of alcohol is that it can lead to the complete dispossession of an entire forest. The study of population dynamics, monitoring and the development of forecasting models are designed to prevent the shades that when you go on for two or three consecutive years, can cause large-scale damage on forests.
Importance of Insects: the wide dissemination of the class and the frequent interaction with the Man involving insects in various areas of interest, in addition to the strictly zoological and natural. The high number of species present in this class has led to the evolution of a specific branch of Zoology, Entomology said, which in turn is divided into different branches of specialization. The complexity of the matter is that, in general, the areas of study for individual consultants focus on a single order, or sometimes on smaller taxonomic groups. This led to the establishment of international academic associations, whose interest focuses on individual taxa (Hemiptera, "" Beetles, "etc.).
harm
The Mediterranean fruit fly, a plague of fruit-growing regions of tropical and temperate calde.La harm insects and perhaps most clearly is associated with this class, but in fact the number of species significantly harmful is negligible compared to the number of useful species or indifferent. But these few species can cause damage on such a scale as to constitute some, the real scourges. The study of insects as factors of damage lies in four areas of interest:
Agroforestry. Are potentially harmful insects that attack the plant species from which man derives utility directly or indirectly. The degree of importance is related to the level of damages, so the number of species actually harmful is reduced substantially. On the other hand, every year there are insects that spend an unspecified species status harmful to a species due to emergencies arising from particular contexts (for imports from other regions, degradation of the ecological balance, etc.).. The most important phytophagous species generally fall into Rincoti orders, the Orthoptera, Lepidoptera, the Diptera, Hymenoptera and Coleoptera.
Food . They are generally all the harmful insects that attack foodstuffs, as they can cause the total destruction of entire games inservibilità or stored in warehouses or accelerate the decomposition of perishable products. Species harmful to food include, in general, among beetles, moths, flies and the Blattoidei. In addition to direct damages should also be considered the risk of sanitation due to the possible transmission of pathogens to humans, often in the case of Blattoidei and Diptera.
Technology. In this area are especially harmful insects xylophagous, which attack the wood work and all its artifacts. In this respect the orders of interest are the Isotteri (termites), are particularly dangerous in the tropics, and beetles (woodworm). Other insects of technological interest are the moths, which attack microlepidotteri scavengers textile products.
sanitation . Medical or veterinary interest are the insects that attack the higher vertebrates, especially the epizootic parasites, predators and endoparasites blood-sucking parasites that attack mammals and birds. These insects are responsible for diseases directly or as vectors of microbial pathogens and viruses. On the interest of sanitation are strictly those insects scavengers of transmitting pathogens. The insects of interest sanitation are part of the above orders Mallofagi, the Anoplura, Diptera and the Sifonatteri.
Utilities
The Ape, the emblem of the usefulness of insects, essential for pollination of many plants and widely bred for the production of miele.Ai insect damage is opposed to the utility of many other species, especially as organizations engaged in the affected ecosystems and in food webs. There are many, however, where the insects are directly useful to man.
Most importantly, dedicated to studies and the increasingly widespread use, the role of insects as their subsidiary bodies. The artropofagi are useful, if not essential, as agents of natural control of arthropods harmful. This role is brought to the fore in the various forms of sustainable agriculture (organic farming, cultivation carried out using the criteria of biological and integrated, etc..) And in the forest sector. Also helpful are some pests when their biological action is made on weeds, such as occurred in the control of Opuntia in Australia, using the Cactoblastis cactorum and Dactylopius Opuntiae. No less important is the role of insect pollinators, including especially in the orders Diptera and Hymenoptera, which are essential for fruiting of many agricultural species, which make use of pollination insects.
The importance of auxiliary insects is so great that they are an economic reality, the so-called biofactories, industrial breeding of insects for use in biological warfare or the struggle biotechnology (eg, male sterile). This area of \u200b\u200bapplication has so far occupied a marginal role, especially at the high cost, uncompetitive against the field of chemical industry, however, is expanding to the growing demand for health environmental and food industries.
In Rangoon, the electric light bug ("electric light bugs") are caught at night, attracted by lanterns, to be served fried in local markets and economic uses ristoranti.Gli were of great importance especially in the past. Before the advent of industrial chemistry, many species were used to obtain substances used for various purposes, such as coloring, lacquer, silk, wax. A prime example is the importance it has had the Bombich Mulberry, whose product, silk, was for centuries the main character of trade between Asia and Europe. The use for economy class, presently covers the API used for the production of honey and wax, and secondly, of royal jelly and propolis.
of marginal importance and local level, but only in appearance, is the use of insects as food, in various populations in Central America, Africa and Asia. It was found that the number of species used as food by human being amounts to over 1400. Some species are considered delicacies real market demand, for example, the Axayacatl in Mexico, from where you get the eggs or caviar ahuautle Mexican and Belostomatidi in Asia. However the most important aspect, in which the same FAO pays particular attention is the potential source of food that the insects can be to curb the problem of malnutrition, the high nutritional value, higher than that of meat and fish contain dried caterpillars, in fact, more than 50% protein, 17% carbohydrate and 15% lipids.
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