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An instar (ˈɪnstɑr, from the Latin īnstar 'form, likeness') is a developmental stage of arthropods, such as insects, between each moult (ecdysis), until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or assume a new form. Differences between instars can often be seen in altered body proportions, colors, patterns, changes in the number of body segments or head width. After shedding their exoskeleton (moulting), the juvenile arthropods continue in their life cycle until they either pupate or moult again. The instar period of growth is fixed; however, in some insects, like the salvinia stem-borer moth, the number of instars depends on early larval nutrition. Some arthropods can continue to moult after sexual maturity, but the stages between these subsequent moults are generally not called instars. For most insect species, an instar is the developmental stage of the larval forms of holometabolous (complete metamorphism) or nymphal forms of hemimetabolous (incomplete metamorphism) insects, but an instar can be any developmental stage including pupa or imago (the adult, which does not moult in insects). The number of instars an insect undergoes often depends on the species and the environmental conditions, as described for a number of species of Lepidoptera. However, it is believed that the number of instars can be physiologically constant per species in some insect orders, as for example Diptera and Hymenoptera. The number of larval instars is not directly related to speed of development. For instance, environmental conditions may dramatically affect the developmental rates of species and still have no impact on the number of larval instars. As examples, lower temperatures and lower humidity often slow the rate of development and that may have an effect on how many molts an insect will undergo - an example of this is seen in the lepidopteran tobacco budworm. On the other hand, temperature affects the development rates of a number of hymenopterans without affecting numbers of instars or larval morphology, as observed in the ensign wasp and in the red imported fire ant.

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Insect

Insects (from Latin insectum) are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (head, thorax and abdomen), three pairs of jointed legs, compound eyes and one pair of antennae. Their blood is not totally contained in vessels; some circulates in an open cavity known as the haemocoel. Insects are the most diverse group of animals; they include more than a million described species and represent more than half of all known living organisms.

Instar

Cicada

The cicadas (sɪˈkɑːdəz,_-ˈkeɪ-) are a superfamily, the Cicadoidea, of insects in the order Hemiptera (true bugs). They are in the suborder Auchenorrhyncha, along with smaller jumping bugs such as leafhoppers and froghoppers. The superfamily is divided into two families, the Tettigarctidae, with two species in Australia, and the Cicadidae, with more than 3,000 species described from around the world; many species remain undescribed. Cicadas have prominent eyes set wide apart, short antennae, and membranous front wings.

Diagonalization of Linear Transformations

Explains the diagonalization of linear transformations using eigenvectors and eigenvalues to form a diagonal matrix.

Revitalisation d'un village alpin en friche, le cas de Mase, Val d'Hérens (VS)

Jean-Pascal Moret

L'abandon des activités agricoles de montagne et les évolutions liées au tourisme de masse ont profondément transformé le territoire des Alpes durant la seconde moitié du XXe siècle. L'impact de ces mutations sur les régions alpines a induit des développements divergents au sein des vallées. Les implantations humaines par plateau d'altitude, originellement connectées entre elles et interdépendantes, ont laissé place à des zones de croissances entourées de vastes espaces en friche. Afin d'offrir un nouveau souffle à ces villages en déclin, l'intervention propose de mettre en relation, par l'intermédiaire d'un élément paysager ayant perdu sa fonction d'irrigation initiale (un bisse), deux tissus illustrant ces caractéristiques différentes. Elle s'articule en deux parties et vient, à l'échelle du village, renforcer l'importance de ce cours d'eau comme colonne vertébrale des activités préexistantes et futures. En amont, un bâtiment public et sa place amorcent la liaison le long du bisse avec la zone des mayens. Dans la partie inférieure, l'implantation des bâtiments cherche à retrouver les particularités qui forment la qualité du tissu existant et l'intensité des relations humaines favorisée par la densité prévalant dans les villages de montagne. La forte économie du sol, la verticalité des volumes et la mixité d'affectation proposent, à l'instar de l'existant, des espaces interstitiels tenus par les masses bâties verticales générant une spatialité variée augmentée par les vues cadrées sur le paysage.

2013