There are many more species in the tropics, especially in rainforests, than in temperate zones. Insects are distributed over every continent and almost every terrestrial habitat. Insects and other bugs that could be confused with them.Whether winged or not, adult insects can be distinguished by their three-part body plan, with head, thorax, and abdomen they have three pairs of legs on the thorax. Adult insects are the only arthropods that ever have wings, with up to two pairs on the thorax. Other terrestrial arthropods, such as centipedes, millipedes, woodlice, spiders, mites and scorpions, are sometimes confused with insects, since they have a jointed exoskeleton. Entomologists to some extent reserve the name "bugs" for a narrow category of " true bugs", insects of the order Hemiptera, such as cicadas and shield bugs. In common speech, insects and other terrestrial arthropods are often called bugs. Insects and other bugs Distinguishing features The English word insect first appears in 1601 in Philemon Holland's translation of Pliny. The Latin word was introduced by Pliny the Elder who calqued the Ancient Greek word ἔντομον éntomon "insect" (as in entomology) from ἔντομος éntomos "cut in pieces" this was Aristotle's term for this class of life in his biology, also in reference to their notched bodies. The word insect comes from the Latin word inseco, from in, "to cut up", as insects appear to be cut into three parts. Human activities are having serious effects on insect biodiversity. Insects are consumed as food in 80% of the world's nations, by people in roughly 3000 ethnic groups. Two species in particular are economically important and were domesticated many centuries ago: silkworms for silk and honey bees for honey. Many insects are ecologically beneficial as predators of pest insects, while a few provide direct economic benefit. Insect pollinators are essential to the reproduction of many flowering plants and so to their ecosystems. ![]() Others are parasitic, and may act as vectors of diseases. Humans regard many insects as pests, especially those that damage crops, and attempt to control them using insecticides and other techniques. Other species communicate with sounds: crickets stridulate, or rub their wings together, to attract a mate and repel other males. Male moths can sense the pheromones of female moths over great distances. Insects can communicate with each other in a variety of ways. Others, such as earwigs, provide maternal care, guarding their eggs and young. Insects are mostly solitary, but some, such as bees, ants and termites, are social and live in large, well-organized colonies. Some species, such as water striders, can walk on the surface of water. Many insects are at least partly aquatic, and have larvae with gills in some species, the adults too are aquatic. Insects are the only invertebrates that can achieve sustained powered flight insect flight evolved just once. The most diverse insect groups appear to have coevolved with flowering plants.Īdult insects typically move about by walking and flying some can swim. Fossilized insects of enormous size have been found from the Paleozoic Era, including giant dragonflies with wingspans of 55 to 70 cm (22 to 28 in). The higher level relationship of the insects is unclear. Insects that undergo three-stage metamorphosis lack a pupa, developing through a series of increasingly adult-like nymphal stages. Groups that undergo four-stage metamorphosis often have a nearly immobile pupa. The immature stages often differ from the adults in structure, habit and habitat. Insect growth is constrained by the inelastic exoskeleton, so development involves a series of molts. Their sense of smell is via receptors, usually on the antennae and the mouthparts. Many insects can hear, using tympanal organs, which may be on the legs or other parts of the body. Insect vision is mainly through their compound eyes, with additional small ocelli. The blood therefore does not carry oxygen it is only partly contained in vessels, and some circulates in an open hemocoel. ![]() Insects breathe air through a system of paired openings along their sides, connected to small tubes that take air directly to the tissues. ![]() The insect nervous system consists of a brain and a ventral nerve cord. Insects are the most diverse group of animals, with more than a million described species they represent more than half of all animal species. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pairs of jointed legs, compound eyes, and a pair of antennae. They are the largest group within the arthropod phylum. ![]() Insects (from Latin insectum) are hexapod invertebrates of the class Insecta. Insects, such as this scorpionfly, have a three-part body: head with large compound eyes and antennae, a thorax with three pairs of legs and often wings, and a segmented abdomen.
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