Insects must their name to the metameric structure of the body [2]. The metamerism of insects and heteronomous type: the body is indeed divided generally into three distinct morphological regions, called head, thorax and abdomen, which are associated appendages such as antennae, legs and wings. The morphological regions are known generically Tagma.
The entire body is enclosed within an exoskeleton, formed from organic materials that give a specific strength. There are stretches of discontinuity in which the integument becomes membranous. In this way the body and appendages are divided into units called segments or somites (if referred to the body) or articles (if the appendices).
The shape, the size and general appearance of the body depend on several factors: many of the dimensions of the order Hymenoptera have Tricogrammatidi 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 [3] and the atlas moth Saturnide Attacus, considered the largest butterfly in the world, has a wingspan of over 25 cm [4]. The shapes vary widely, also including those of the convoluted Rincoti coccidia where it can disappear altogether differentiation of morphological regions of the body and appendices, except for buccal apparatus.
Exoskeleton [edit]
Main Exoskeleton see the entry of insects.
The sclerites of the thorax in a Calcidoide Hymenoptera.
The sclerites of the thorax in a Calcidoide Hymenoptera.
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 is 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 scattered hairs, bristles, scales, and sculptures that are often essential for taxonomic.
Cape [edit]
Main article: Head of insects, insect antenna and Mouthparts insects.
Chief of Orthoptera.
Chief of Orthoptera.
a: antenna
b: ocelli
c: Summit
d: compound eye and
: occiput
f: gena
g: h pleurostoma
:
the mandible: labial palp
j: maxillary palps
k jaw
l: lip top
m: n clypeus
: foot
The head is the region composed of the first six somites that merge into a structure where you lose the original metamerism. The first three somites form the procefalo, the next three the gnatocefalo [5]. 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.
external cephalic structures have two main purpose: the perception of sensory stimuli and the first supply phase (taking, processing and food ingestion). These facilities generally include a pair of antennae, two compound eyes, three 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, three in number. The
commitment are 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 to take solid food and a shredding them. Many taxonomic groups have However, 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 [edit]
Main articles: Chest of insects, insects and Paw Ala insects.
Side view of the thorax of an orthopteran.
Side view of the thorax of an orthopteran.
to: neck
b: pronotum
c: mesoepisterno
d: suture and pleural
: mesoepimero
f: metaepisterno
g: h metaepimero
: coxa
i: trochanter
j: k
femur: tibia
l: tarsus
m: pretarso
The chest comes from the turning 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 ridge, called back, or known tergite;
* two sides, called pleura;
* a ventral sternum or Stern said.
In the terminology is used to specify both the thoracic segment and the area to which it refers, 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 the individual sclerites and appendages. The morphology
of 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).
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 the adhesion 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 sliders. Morphological and anatomical adaptations are often designed to function, 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, una ventrale, in continuità con le pleure. Nella maggior parte degli Insetti la continuità è interrotta da un sistema di articolazioni composto da tre scleriti pterali e due scleriti toracici differenziati dalle pleure. Le ali degli Insetti sono prive di muscoli intrinseci: il movimento si deve all'azione di muscoli dislocati nel torace. L'ala è percorsa da condotti, detti nervature o vene in cui passano l'emolinfa, nervi e trachee. Il decorso delle nervature è un importante elemento di determinazione tassonomica in alcuni ordini.
La morfologia alare varia molto secondo il gruppo sistematico. In generale sono membranose, talora sono più o meno sclerificate. Le anteriori hanno spesso uno sviluppo maggiore e possono essere presenti specifici organi di collegamento per la sincronizzazione del movimento. La superficie alare è distinta morfologicamente in tre regioni, dette rispettivamente remigante, anale e jugale; la prima ha il maggiore sviluppo e la maggiore robustezza. La funzione primaria è quella del volo, tuttavia gli adattamenti possono alterare questa funzione fino a farla perdere del tutto a favore di altre finalità, trasformando le ali in organi di protezione, regolazione dell'equilibrio, ecc.
Addome [modifica]
Per approfondire, vedi la voce Addome degli insetti.
Addome di una femmina di Ortottero.
Addome di una femmina di Ortottero.
a: tarso
b: femore
c: tibia
d: urotergo And
: urosterno
f: Seeking
g: ovipositor
The abdomen is the region in which they are established morphological organs of reproduction. Consistency more delicate than the thorax, is composed of 11 segments, such uriti, but the XI [6] 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 membrane intersegmental, an elastic structure and flexible, allowing the expansion of the region and some mobility.
The abdominal appendages are usually very noticeable compared to the 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 that take la denominazione di ovopositore di sostituzione.
Altre appendici diffuse in molti Insetti sono i cerci, inseriti ai lati dell'ultimo urite. Rudimentali o assenti negli ordini meno evoluti, in alcuni gruppi sistematici possono raggiungere un notevole sviluppo. Nelle larve sono spesso presenti processi che svolgono varie funzioni. Le più diffuse sono le pseudozampe delle larve polipode.
Anatomia [modifica]
Rappresentazione schematica dell'anatomia di un insetto femmina (non sono riportati i sistemi respiratorio, secretore e muscolare).
Rappresentazione schematica dell'anatomia di un insetto femmina (non sono riportati i sistemi respiratorio, secretore e muscolare).
1. Cerebro
2. Ganglion ipocerebrale
3. Body allatum
4. Body pharyngeal
5. Aorta
6. Ganglion stomach
7. Craw
8. Gizzard
9.
heart valve 10. Mesentery
11. Emocele
12. Ventriculitis
13. Heart
14. Ostiolo
15. Rectum
16. Ano
17. Vagina
18. Frontal ganglion
19. Track periesophageal
20. Epifaringe
21. Pharynx
22. Gnatocerebro
23. Esophagus
24. Ventral ganglia
25.
pyloric valve 26. Malpighian tubes
27. Proctodeo
28. Ovariolo
29. Ovary
30. Spermateca
Rispetto ai Vertebrati, Insetti e Artropodi invertono la dislocazione dei sistemi assili: l'apparato circolatorio e il sistema nervoso periferico assumono rispettivamente una posizione dorsale e ventrale, mentre l'apparato digerente si disloca in posizione centrale. Pur mantenendo alcune analogie, la struttura anatomica differisce marcatamente da quella dei Vertebrati anche se spesso si tende a mutuare per attinenza la terminologia specifica di organi e apparati.
Endoscheletro [modifica]
Per approfondire, vedi la voce Endoscheletro degli insetti.
L'endoscheletro consiste in un'estensione interna dell'esoscheletro, finalizzata a favorire l'attacco dei muscoli e il sostegno degli organi. It consists of a set of internal processes, and development of various forms.
located in the head and the tentorium, the more training dell'endoscheletro, 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 there are a couple of Fragma (back), one of apodemi (side) and Furche (Learn and ventral). Abdomen, finally, are reduced to apodemi dorsal and ventral development.
muscle system [edit]
muscles of insects are almost all type of striated stick to the cuticle or exoskeleton dell'endoscheletro by fibrils not contrattili (tonofibrille), assimilabili ai tendini dei Vertebrati. Il loro numero è elevato, dell'ordine di migliaia. Si distinguono in scheletrici e viscerali: i primi hanno denominazioni derivate dal loro percorso o dalla loro funzione e sono generalmente pari e simmetrici. Sono responsabili dei movimenti delle appendici e delle regioni morfologiche del corpo, perciò sono detti anche somatici. La muscolatura viscerale è associata agli organi interni ed è solo in parte costituita da fibre muscolari lisce.
Apparato digerente [modifica]
Per approfondire, vedi la voce Apparato digerente degli insetti.
L'apparato digerente degli Insetti è un tubo che parte dall'apertura boccale e termina in quella 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 alle funzioni di ingestione e prima elaborazione dell'alimento e, in alcuni Insetti, al temporaneo immagazzinamento. Parte dall'apertura boccale e termina in corrispondenza della valvola cardiaca dove confluisce nel mesentero. Procedendo in senso cefalo-caudale, si divide nelle seguenti sezioni: cavità orale, faringe, esofago, ventriglio, quest'ultimo sviluppato soprattutto negli insetti ad apparato boccale masticatore. Lo stomodeo può presentare un diverticolo, l'ingluvie, che in alcuni Insetti raggiunge dimensioni tali da occupare anche parte dell'addome. Le funzioni dell'ingluvie possono avere una specificità tale da giustificare particolari denominazioni (es. borsa melaria nelle Api, stomaco sociale nelle Formiche, borsa del sangue nelle Mosquitoes).
The mesentery is the site where digestion takes place itself, with the demolition of the enzyme macromolecules and 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, in As you merge the Malpighian tubes. It begins at the pyloric valve, but in some taxonomic groups the mesentery and the dead-end and therefore has a break in 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 histological nature of stomodeo and proctodeo is ectodermal, the mesentery is probably entodermica [7] [8]. The walls of
stomodeo proctodeo and are composed, from the inside out, by a cuticular layer, called intimate by an epithelial layer, a membrane baseline by a muscular coat consisting of a bundle of internal longitudinal muscles and an outer circular muscles and, finally, a peritoneal tunic of connective tissue. The muscular tunic includes the stomodeo, a bundle of internal 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 tunica intestine.
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 body has the role 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 adjustment is precisely the honeydew-producing insects, excrement liquid high sugar content.
Respiratory [edit]
Main article: Respiratory system of insects. Stigma abdominal
a Beetle. Stigma abdominal
a Beetle.
transport oxygen to the cells are not entrusted to the bloodstream [9], so the insects are marked differences from the circulatory and respiratory systems of vertebrates.
The respiratory system of insects reflects some of 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 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. Tracheole have the smaller diameter of the order of several microns.
In many insects the tracheae can dilarsi in air sacs, whose function is to build up reserves of air or act as a hydrostatic or aerostatic bodies. Circulatory
[edit]
Main article: Circulatory system insects.
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 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, which is entrusted to the respiratory system in insects [9]. The hemolymph was instead charged with transporting nutrients and catabolites and the immune system. The
emocele is divided da due diaframmi longitudinali in tre cavità intercomunicanti. Formati da tessuto connettivo e muscolare, hanno un movimento peristaltico che favorisce la circolazione verso la zona caudale e l'ingresso nella parte posteriore del vaso dorsale pulsante. Il vaso dorsale si differenzia in due tratti, uno posteriore (cuore) e uno anteriore (aorta). Il cuore è suddiviso in camere intercomunicanti (ventricoliti), ciascuna provvista di due valvole (ostioli), attraverso le quali vaso dorsale comunica con l'emocele. Il sistema muscolare associato al vaso dorsale imprime le pulsazioni che spingono il sangue verso la regione cefalica. Altri organi pulsanti accessori sono localizzati nelle appendici e favoriscono la circolazione in organi che offrirebbero una maggiore resistance.
The hemolymph of insects differs considerably 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 [edit]
Main article: Apparatus insect nervous. Schematic representation of the nervous
of Insects. Schematic representation of the nervous
of Insects.
P: protocerebrum
D: deutocerebro
T: tritocerebro
G: gnatocerebro
CV:
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.
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 mediator, acetylcholine. Many insecticides, as acetylcholinesterase inhibitors also have neurotoxic effects on vertebrates.
The central nervous system has metameric organization: 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 the organs and 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 side and innervate the stretch of stomodeo iniziale dell'apparato digerente. Il secondo parte dai gangli della catena ventrale e innerva le trachee e gli stigmi. Il terzo, infine, parte dall'ultima coppia della catena ventrale e innerva il proctodeo e gli organi genitali.
Il sistema nervoso periferico comprende gli assoni dei neuroni motori, che innervano la muscolatura striata, e i neuroni sensoriali associati ai recettori. Si sviluppa in tutte le parti del corpo ed è associato ai gangli del sistema nervoso centrale.
Apparato escretore [modifica]
Per approfondire, vedi la voce Apparato escretore degli insetti.
L'apparato escretore provvede all'eliminazione delle sostanze di rifiuto (cataboliti). È composto da organi localizzati (tubi Malpighian) and disseminated (nephritis or nefrociti). 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 in varying numbers 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
nefriti sono gruppi sparsi di cellule, a volte isolate, associati allo stomodeo, alle ghiandole salivari e al vaso dorsale. La loro funzione è quella di regolare il pH dell'emolinfa e agire come organi escretori intermedi, trasformando i cataboliti in forme che saranno poi eliminate dai tubi malpighiani.
Apparato secretore [modifica]
Per approfondire, vedi la voce Apparato secretore degli insetti.
Secrezioni cerose della larva di un Coccinellide.
Secrezioni cerose della larva di un Coccinellide.
Gli Insetti dispongono di un apparato ghiandolare complesso, distinto in un sistema esocrino, composto da ghiandole a secrezione esterna, e in uno endocrino, composto da ghiandole a secrezione interna.
Il sistema endocrino è formato da cellule e organi che hanno relazione con il sistema nervoso. Regola la biologia dell'Insetto e raggiunge livelli di complessità organizzativa paragonabili a quello degli animali superiori. Una particolarità che differenzia gli Insetti dai Vertebrati consiste nell'assenza di funzioni di secrezione endocrina nell'apparato riproduttore. Le ghiandole endocrine d'importanza basilare si identificano in quattro strutture: il sistema endocrino cerebrale, i corpi cardiaci, i allati e le ghiandole protoraciche. La funzione primaria svolta da queste ghiandole è la regolazione dello sviluppo postembrionale, ma singolarmente queste strutture controllano anche altri processi biologici.
Il sistema endocrino cerebrale consists of nerve cells in 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. These accumulate hormone modify the brain 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 il torace. La loro funzione primaria consiste nel rilascio, dietro stimolo dell'ormone cerebrale, dell'ecdisone, che induce la muta.
Il sistema esocrino è composto da ghiandole uni- o pluricellulari. Queste ultime sono a loro volta semplici o composte, le prime con un unico dotto escretore comune a tutte le cellule, le altre con un dotto escretore per ogni cellula confluente un serbatoio comune. Altre classificazioni possono riguardare la posizione e la distribuzione nel corpo.
Per quanto riguarda la natura del secreto, gli Insetti sono provvisti di una grande varietà di ghiandole, molte delle quali sono tuttavia specifiche di uno o più gruppi sistematici. Ghiandole che svolgono la stessa funzione possono inoltre differire per localizzazione, struttura e sviluppo in funzione delle varie categorie sistematiche. Una trattazione dell'anatomia e della fisiologia del sistema esocrino non può prescindere da una semplificazione riduttiva, data l'estrema eterogeneità. Per gli approfondimenti si rimanda ai singoli gruppi sistematici.
Fra i sistemi ghiandolari di maggiore frequenza si citano i seguenti:
* Ghiandole accessorie dell'apparato genitale. Presenti in entrambi i sessi, secernono sostanze che in genere sono coadiuvanti della riproduzione: il secreto dei maschi ha funzioni trofiche nei confronti degli spermatozoi, quello delle femmine interviene, in genere, nella dinamica dell'ovideposizione. Non mancano funzioni specifiche estranee alla reproduction, as in the case of the venom glands of Hymenoptera Aculeate. *
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. * Glands
ceripare. Common among the Hymenoptera, the Rincoti Omotteri and some beetles, are usually widespread in the integument and secrete the wax. The secret is used for various purposes, including the protection is often of the body. *
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, the second induces the formation 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.).
* Glands sericipare. Present in many orders, show a considerable variety in the location and structure. Secrete the silk used, as appropriate, for the construction of cocoons, nests, ooteche, for the protection of the body, etc..
reproductive system [edit]
Main article: reproductive system of insects.
Female Icneumonide during oviposition.
Female Icneumonide during oviposition.
insects, hermaphroditism was found only in Icerya purchasi and in some Diptera [10], so the reproductive system differs in two distinct sexes from embryonic homologous structures.
gonads, of mesodermal origin, are the venue for holding the gametogenesis. They differ in the testes (male) and in the ovary (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. for their particular structure is difficult Pest 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 submit 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, where sperm are kept in the interval 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 dipendono essenzialmente dal tipo ghiandolare. Le ghiandole più comuni sono dette colleteriche e il loro secreto è usato come coadiuvante dell'ovideposizione, come collante per le uova, per la costruzione di ooteche, ecc. Altre ghiandole, dette spermofile, secernono un fluido nutritivo per gli spermatozoi conservati nella spermateca. Negli Imenotteri Apocriti sono presenti anche le ghiandole velenifere: il loro secreto, emesso con l'ovopositore o con l'aculeo, ha un'azione associata all'ovideposizione oppure integra la funzione secondaria di strumento di offesa e difesa nelle femmine sterili.
Gli organi genitali esterni si differenziano in genere come processi degli urosterni costituendo l'armatura genitale, importante elemento di determinazione taxonomy. 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 which 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 adaptations of the last uriti, ovipositor, which are called substitutes. The ovipositor in Hymenoptera Aculeate undergoes anatomical and functional adaptation that turns it into an instrument of aggression and defense in this case is called a sting or a sting.
Biology [edit]
The long evolutionary history, the high number of species, the ability to adapt to even extreme living conditions, are a group of Insects Systematic biology heterogeneous. An organic treatment that covers the various aspects, from physiology to the biological cycle, from feeding to reproduction, ethology from the reports in general, can only be brief and general. It therefore refers to specific sections and discussion individual taxonomic groups to the appropriate depth.
Biological cycle [edit]
The life cycle of an insect can take, depending on the species, a few days to several years and, often, its development is closely related to environmental factors of natural climate (particularly temperature ) and nutrition. This means that insects can adapt to multiple environments, including the coldest regions on Earth, using biological measures such as the winter in a state of diapause and seasonal migration.
The life cycle is said monovoltino accomplished if only one generation per year, if polivoltino takes several generations. The number of generations is not is related to the length of the cycle, as a population in different stages of development can coexist with overlapping generations (eg aphids). Conditions of high specificity can synchronize your cycle with that of a species of plant or animal from which the insect depends for its nutrition. In these cases you can have the concentration and timing of reproductive events and development, with well-defined generations (eg, olive moth). Playing
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Coupling of two grasshoppers.
Coupling of two grasshoppers.
Reproduction is typically by sexual contact (anfigonia), with the coupling between separate sexes and fertilization 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).
are common to 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 the 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 [11] [12]. 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 [12].
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 the other hand, sex is determined by the ratio between anfigonia and haploid parthenogenesis: females arise after fertilization, the males by parthenogenesis.
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 [edit]
Main article: postembryonic development in insects.
The flicker of a cicada.
The flicker of a cicada.
postembryonic development is based on the metamorphosis of insects, discontinuous sequence of physical changes that, starting from the egg leads to the formation of the adult.
in insects and, more generally, in arthropods, one must distinguish the growth ponderale (incremento del peso), che procede in modo continuo, dall'accrescimento lineare (incremento delle dimensioni), che è invece discontinuo. A causa della rigidità dell'esoscheletro, l'aumento di peso in un insetto giovane non è accompagnato da un aumento di dimensioni; ad un certo punto, la vecchia cuticola (exuvia) si lacera e l'individuo ne fuoriesce con una nuova, in grado di contenere l'aumento di dimensione. Il fenomeno è detto muta.
Alla muta può accompagnarsi anche la metamorfosi, ossia una trasformazione fisica che non si limita solo all'aumento delle dimensioni. Accrescimento e metamorfosi sono regolati da meccanismi neurormonali che si riassumono nell'interazione tra due ormoni, l'ecdisone e la neotenina. L'ecdisone stimola la genesi della nuova cuticola, perciò è il segnale biologico che avvia una nuova muta. La neotenina, invece, inibisce la comparsa dei caratteri dell'adulto, che restano latenti sotto forma di abbozzi. In presenza di neotenina, l'ecdisone stimola la muta senza metamorfosi; in assenza di neotenina l'ecdisone stimola la muta accompagnata dalla metamorfosi.
La classificazione dei tipi di metamorfosi verte su schemi per i quali non c'è uniformità di orientamento fra gli Autori. Le fasi dello sviluppo ontogenetico possono infatti essere interpretate sotto differenti aspetti e la terminologia non sempre è usata in modo appropriato. Per ulteriori approfondimenti si rimanda ai dettagli descritti nella voice deepening.
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, except for a nervous and circulatory system. The magnitude of the changes is such that, at this stage, the state of immobility of the insect. The wing buds are internal and only appear 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 and can be identified in an adult form farata. Farata phase is a stage of transition, following the last changes, during which the adult has not yet abandoned the Exuvia in other words, an individual in the form farata is an adult who apparently looks like a mobile pupa.
In incomplete metamorphosis, which is identified with the heterometabolous, the juvenile stage is called nymphs and differs from the adult only the smaller 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. This kind of metamorphosis of insects is just winged or secondarily wingless, less evolved, whose orders are included in the cohort of Esopterigoti.
The two previously described adds a third type, called ametabolic, in which, in reality, there is no metamorphosis. The ametabolic occurs in primitive wingless insects, in which case the juvenile stages present no morphological difference compared to adults, if not in size, and development is carried out with mute without any metamorphosis. The ametabolic is only proper to the order of (Tisanuri) and not to be confused with pseudoametabolia, 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 particular ethology and is reflected by both nell'olometabolia is nell'eterometabolia. Power
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A larva of Crisopa as "sucks" an aphid. A larva of
Crisopa as "sucks" an aphid.
The diet of insects are among the most varied and can change drastically even during the development of a individual (and holometabolous paurometaboli). The majority of insect trophic relationships with the plants or animals, or clear a system omnivorous. Insects are also common detritivores or, more generally scavengers, there are 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 differ monofaghe species, 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..
fitomizi The insects are biting-sucking mouthparts to feed on and at the expense of the juices or sap prepared epidermal cell phones. A particular group is represented by insects knot, which develop within the affected organ histological alteration (floating). In this case the pest comes close better to 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 true predation (eg, Ditiscidi 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 insects zoofago regime, in fact, has trophic relationships with other arthropods and, in particular, with other insects. In these cases, the trophic relationships are identified with the real predation or the parasitoid, while cases of true parasitism 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.
A special diet is that of glicifagi. These insects feed at the expense of sugars and generally used 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 Insects are important as pollinators, as in the carriage of pollen, and thus promote cross-pollination.
Some diets are particularly complex and do not have a place well-defined: for example, some parasitoids of Hymenoptera insects knot can become pests when, once the victim, complete their growth 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 [edit]
Two massive nests built by termites.
Two massive nests built by termites.
For the reasons stated above, the behavioral aspects of this class are heterogeneous and diverse, sometimes with non-negligible levels of complexity. The behaviors may represent peculiarities own one or a few species or taxonomic groups to spread wider.
One of the most interesting aspects of ethology of insects is undoubtedly that of social insects, species that have developed a complex level of gregariousness organized caste and 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, are intended to determine the success of biological species in the sacrifice of the individual in favor of the entire community. The best known examples of social interaction, involving mostly the Isotteri and Hymenoptera, plus a wide range of social aggregation phenomena not represented in the most orders, with different levels of complexity with regard to internal relationships.
Ethology of Insects show interesting and varied aspects of behavior with regard to food, building nests, reproduction, migration, communication between individuals of the same species, the relationship with organisms of different species, 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 [edit] The
Bombich odd cause extensive defoliation during his grades cyclical. The odd
Bombich causes extensive defoliation during his grades cyclical.
Even with regard to population dynamics, occurring on different models, which often interferes on the man disguising or simplified 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 occurs especially in the agro-systems, in which the loss of biodiversity creates imbalances that benefit their own species with high 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 shows exponential growth rates, by virtue of strong biotic potential, the availability of resources and lack of nutrients impact of natural factors control;
* height: the population increases with decreasing increments until it reaches a maximum, at which stage they become restrictive factors of natural control of population: intraspecific competition, reduced fertility, increased disease and population of antagonists;
retrogradation *: Due to the high incidence of natural control factors, mortality increases significantly and the population collapses more or less rapidly to equilibrium values \u200b\u200bgiven on 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 [edit]
The widespread class and 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.
harmfulness [edit]
The Mediterranean fruit fly, a plague of fruit-growing regions of tropical and warm temperate.
The Mediterranean fruit fly, a plague of fruit-growing regions of tropical and warm temperate.
The harmfulness of Insects is perhaps the most obvious aspect that 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 contributing to damage in four places 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 to a species of harmful due to emergencies arising from particular contexts (for imports from other regions, degradation of the ecological balance, etc.).. The most important phytophagous species are generally Rincoti, Orthoptera, Lepidoptera, Diptera, Hymenoptera and Coleoptera.
* Agribusiness. They are generally harmful to all 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. The species are generally harmful to food Coleoptera, Lepidoptera, Diptera and Blattoidei. In addition to direct damages must also consider the sanitary risk associated with possible transmission of pathogens to humans, often in the case of Blattoidei and Diptera.
* Technology. In this area are especially harmful insects that attack wood xylophagous from work and all its artifacts. In this respect the orders of interest are the Isotteri (termites), are particularly dangerous in the tropics, and the beetles (Worms). 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, particularly parasites epizootic, hematophagous endoparasites and predators 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 possible vectors of pathogenic microorganisms. The insects of interest sanitation are part of the above orders Mallofagi, the Anoplura, Diptera and the Sifonatteri.
Utilities [Edit]
the bee, the emblem of the usefulness of insects.
the bee, the emblem of the usefulness of insects.
the insect damage is opposed to the utility of many other species, especially as organizations involved in included in the ecosystem and food webs. The direct benefit of many insects, however, is expressed in the following cases: *
Artropofagi: useful, if not essential, as agents of natural control of arthropods harmful. This role is enhanced in various forms of sustainable agriculture (organic farming, cultivation carried out using the criteria of biological and integrated, etc..) And in the forest sector. *
pests useful: pests become useful when their biological action is made on weeds, such as occurred in the control of Opuntia weeds in Australia, using the Cactoblastis cactorum and Dactylopius Opuntiae.
* Insect pollinators: glicifagi many insects, including especially in the orders Diptera and Hymenoptera are essential for fruiting of many agricultural species, which make use of pollination insects.
* used in: even if it is a minor aspect, we should mention the use of certain species for food in some populations. *
economic uses of great importance, especially in the past was the use of certain species for the extraction of certain substances used for various purposes, such as coloring, lacquer, silk, wax. The use for economy class, however, affect the API, used for the production of honey, royal jelly, propolis and wax.
Among the economic uses are also mentioned the biofactories, factory farming of Insects to be used in biological or biotechnology in the fight (ie 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 due to growing demand for environmental health and food industries.
Finally recalled the interest charged by Insects hobby in the field as they are sought is subject to the installation of entomological collections for nature photography. Taxonomic
[edit]
In older classifications the class Insecta, Hexapoda synonymous, also included several orders of primitively wingless arthropods. Latest revisions give the name to a group Hexapoda systematically higher, elevated to the rank of Superclass, in which there is a distinction between two classes: the first, Paraentomata is identified in a polyphyletic group comprising those who were previously regarded as the most primitive orders Insects of the second, Euentomata, properly include Insects detti, corrispondente ad un raggruppamento monofiletico. La classificazione all'interno della classe si basa fondamentalmente sulla metamorfosi e sulla morfologia alare. Va in ogni caso ribadito che la sistematica degli Insetti è in continua evoluzione a causa dell'elevato numero di specie e della continua acquisizione di nuove conoscenze, soprattutto nel campo della filogenesi.
L'inquadramento sistematico della classe si può riassumere nel seguente schema:
* Superclasse Hexapoda (o Entoma). Compresa nel subphylum Mandibolata o Antennata, a sua volta facente parte del phylum Arthropoda. Si suddivide in due raggruppamenti sistematici:
* Paraentoma. Raggruppamento artificiale, in quanto polifiletico, include primitive insects and is divided into three subclasses: Oligoentomata (comprising Collembola) Mirientomata (including the Protura) Polientomata (comprising Diplura).
* Insecta Euentomata or proper. Monophyletic grouping systematically elevated to the rank of class. It is divided taxonomically into two subclasses based on the presence of the wings as a primitive character: *
Apterygota. Subclass includes the primitive wingless insects and ametabolic. *
Pterygota. Subclass includes the winged or secondarily wingless insects which undergo a metamorphosis during the post-embryonic development.
Notes [edit]
1. ^ Tremblay, op. cit. p. 11.
2. Insect Insecta ^ derives from Latin, from the greek entomological entomological. In both cases the etymology refers to the segmentation of the body.
3. ^ Stanek. Op cit., P. 270.
4. ^ Stanek. Op cit., P. 377.
5. ^ Servadei, Zang, Masutti. Op cit., Pp. 18-19.
6. ^ By convention, uriti are marked with a Roman numeral sequence, starting from the front
7. ^ Servadei, Zang, Masutti. Op cit., P. 109.
8. ^ Tremblay. Op cit., P. 51.
9. ^ Ab apneustici Insects are the exception, without tracheal spiracles, in which the transport of gas is given all'emolinfa.
10. ^ Servadei, Zang, Masutti. Op cit., P. 89.
11. ^ Tremblay. Op cit., P. 50.
12. ^ Ab Servadei, Masutti, Zang. Op cit., P. 105.
Bibliography [edit]
* Ermenegildo Tremblay. Applied entomology. Volume I. 3. Napoli, Liguori Editore, 1985. ISBN 88-207-0681-4
* Servadei Antonio, Sergio Zang, Louis Masutti. General and Applied Entomology. Padua, CEDAM, 1972.
* Guido Grandi. Institutions of general entomology. Bologna, Calderini, 1966. ISBN 8870190846 * Aldo
Pollini. Handbook of applied entomology. Bologna, Edagricole, 2002. ISBN 8850639546 *
Vincent B. Wigglesworth. Insect Physiology. (In (EN)) London, Meuthuen & Co. LDT, 1934.
* Václav Jan Staněk. Enciclopedia illustrata degli insetti. Elisabetta Ghisotti Steinman (Trad. it.). Praga, Artia (Ed. it. Librerie Accademia) [1970], 1978. ISBN 0600030857
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