During the embryonic stage of many insects and the postembryonic stage of primitive insects, 11 abdominal segments are present. Most insects, however, lead short lives as adults, and rarely interact with one another except to mate or compete for mates. Some insects, such as the mayflies, feed only in the immature or larval stage and go without food during an extremely short adult life. The nervous system of an insect can be divided into a brain and a ventral nerve cord. [36]:9, Several unidentified grasshoppers stridulating, International Union for Conservation of Nature, "Tropical forests: their richness in Coleoptera and other arthropod species", "Insects could be the key to meeting food needs of growing global population", "What is a bug? [36]:186 Their flight muscles are able to contract multiple times for each single nerve impulse, allowing the wings to beat faster than would ordinarily be possible. The larvae reacted to the touch of the heated probe with a stereotypical rolling behavior that was not exhibited when the larvae were touched by the unheated probe. Water beetles and water bugs have legs adapted into paddle-like structures. [120] The largest flying insects today are much smaller, with the largest wingspan belonging to the white witch moth (Thysania agrippina), at approximately 28cm (11in).[121]. Such a mimicry complex is referred to as Batesian. In this sense, Insecta sensu stricto is equivalent to Ectognatha.
It is difficult to assess long-term trends in insect abundance or diversity because historical measurements are generally not known for many species. There are special hobbyist magazines such as "Bugs" (now discontinued). Insects live in nearly every habitat, and its estimated that there are currently 10 quintillion insects on the globe. [140] Because insects usually receive benefit for the pollination in the form of energy rich nectar it is a grand example of mutualism. Due to the abundance of insects and a worldwide concern of food shortages, the Food and Agriculture Organization of the United Nations considers that the world may have to, in the future, regard the prospects of eating insects as a food staple. Instead, the insect respiratory system uses a system of internal tubes and sacs through which gases either diffuse or are actively pumped, delivering oxygen directly to tissues that need it via their trachea (element 8 in numbered diagram). The following represents the best-supported monophyletic groupings for the Insecta. In some cultures, insects, especially deep-fried cicadas, are considered to be delicacies, whereas in other places they form part of the normal diet. A few species of ocean-skaters in the genus Halobates even live on the surface of open oceans, a habitat that has few insect species. With each molt, nymphs grow larger and become more similar in appearance to adult insects. Some of the feather-winged beetles and parasitic wasps are almost microscopic, while some tropical forms such as the hercules beetles, African goliath beetles, certain Australian stick insects, and the wingspan of the hercules moth can be as large as 27 cm (10.6 inches). As of 2009, no evidence suggests the insects were a particularly successful group of animals before they evolved to have wings.
Neoptera can further be divided into incomplete metamorphosis-based (Polyneoptera and Paraneoptera) and complete metamorphosis-based groups. [36]:328348[36]:400[150][151], Medical uses. One of the most famous examples, where the viceroy butterfly was long believed to be a Batesian mimic of the inedible monarch, was later disproven, as the viceroy is more toxic than the monarch, and this resemblance is now considered to be a case of Mllerian mimicry. [7] Many insects are considered ecologically beneficial as predators and a few provide direct economic benefit. The oldest insect fossila mandible (or jaw) found in Scotlandis between 408 and 438 million years old. [95] Some fireflies of the genus Photuris mimic the flashing of female Photinus species to attract males of that species, which are then captured and devoured.
[136] This sort of protective coloration is common and widespread among beetle families, especially those that feed on wood or vegetation, such as many of the leaf beetles (family Chrysomelidae) or weevils. The earliest vertebrates on land existed 400 million years ago and were large amphibious piscivores. LiveScience - 20 Startling Facts About Insects, insect - Children's Encyclopedia (Ages 8-11), insect - Student Encyclopedia (Ages 11 and up).
Insects are also used in medicine, for example fly larvae (maggots) were formerly used to treat wounds to prevent or stop gangrene, as they would only consume dead flesh.
There is extensive variation among different orders, life stages, and even castes in the digestive system of insects. [40] Phasmatodea and Embiidina have been suggested to form the Eukinolabia. Traditional morphology-based or appearance-based systematics have usually given the Hexapoda the rank of superclass,[36]:180 and identified four groups within it: insects (Ectognatha), springtails (Collembola), Protura, and Diplura, the latter three being grouped together as the Entognatha on the basis of internalized mouth parts.
These tubules remove nitrogenous wastes from the hemolymph of the insect and regulate osmotic balance.
The anterior segment, closest to the head, is the prothorax, with the major features being the first pair of legs and the pronotum. Predators that eat poisonous butterflies and moths may become sick and vomit violently, learning not to eat those types of species; this is actually the basis of Mllerian mimicry. For example, because of its small size, short generation time and high fecundity, the common fruit fly Drosophila melanogaster is a model organism for studies in the genetics of eukaryotes.
Estimates of the total number of insect species, or those within specific orders, often vary considerably.
This worm-like form can be one of several varieties: eruciform (caterpillar-like), scarabaeiform (grub-like), campodeiform (elongated, flattened and active), elateriform (wireworm-like) or vermiform (maggot-like).
This can allow an insect to return unerringly to a single hole a few millimeters in diameter among thousands of apparently identical holes clustered together, after a trip of up to several kilometers' distance. The majority of insects are small, usually less than 6 mm (0.2 inch) long, although the range in size is wide. They are important, too, as pheromones, especially in social insects. For example, when moving slowly, turning, avoiding obstacles, climbing or slippery surfaces, four (tetrapod) or more feet (wave-gait[127]) may be touching the ground.
Insects that undergo three-stage metamorphosis lack a pupal stage and adults develop through a series of nymphal stages. [93] Certain predatory and parasitic insects can detect the characteristic sounds made by their prey or hosts, respectively. Some entomologists suggest that the wings are from paranotal lobes, or extensions from the insect's exoskeleton called the nota, called the paranotal theory.
"Natural history of the Neotrobical arboreal ant, "Biocontrol Network Beneficial Insects", "UN: Insects are 'food of the future' (video)", "How AgriProtein makes chicken food from maggots", "Insects as an Alternative Source for the Production of Fats for Cosmetics", "From Pest to Pot: Can Insects Feed the World? 2019.
Microscopic projections from the midgut wall, called microvilli, increase the surface area of the wall and allow more nutrients to be absorbed; they tend to be close to the origin of the midgut. Some insects advertise their presence to the other sex by flashing lights, and many imitate other insects in colour and form and thus avoid or minimize attack by predators that feed by day and find their prey visually, as do birds, lizards, and other insects. For the first step, the middle right leg and the front and rear left legs are in contact with the ground and move the insect forward, while the front and rear right leg and the middle left leg are lifted and moved forward to a new position.
[61]:13, The thorax is a tagma composed of three sections, the prothorax, mesothorax and the metathorax. Bombus terrestris, for example, exhibit a faster learning curve for visiting unfamiliar, yet rewarding flowers, when they can see a conspecific foraging on the same species. Some species of wasp always provide five, others twelve, and others as high as twenty-four caterpillars per cell.
[36]:142[90]. Food safety laws in many countries do not prohibit insect parts in food, but rather limit their quantity. It can be divided into the foregut, midgut and hindgut. Insectivorous insects, or insects that feed on other insects, are beneficial to humans if they eat insects that could cause damage to agriculture and human structures. Some species of insect that are submerged also have adaptations to aid in respiration. 
Insects are mostly solitary, but some, such as certain bees, ants and termites, are social and live in large, well-organized colonies. [118], Insects are the only group of invertebrates to have developed flight. The number of caterpillars is different among species, but always the same for each sex of larva. In many of the more primitive orders of insect, the immature stages are spent in an aquatic environment.
Over time, this has led to complex groups of coevolved species.
[143][144], Although pest insects attract the most attention, many insects are beneficial to the environment and to humans. This greatly increases plants' ability to cross-pollinate, which maintains and possibly even improves their evolutionary fitness. [80][81], The majority of insects hatch from eggs. [153], Insects play important roles in biological research.
[46] E. O. Wilson has estimated that the number of insects living at any one time are around 10 quintillion (10 billion billion).[47].
Diversity of insects from different orders. [15][18] In the narrowest circumscription, insects are restricted to hexapods that are either winged or descended from winged ancestors. They pollinate plants, decompose plant and animal matter, and are themselves a source of food. The terminal portion of the ejaculatory duct may be sclerotized to form the intromittent organ, the aedeagus. In contrast to eggs of other arthropods, most insect eggs are drought resistant.
[63], At least some insects have nociceptors, cells that detect and transmit signals responsible for the sensation of pain.
Globally, averages of these estimates suggest there are around 1.5 million beetle species and 5.5 million insect species, with about 1 million insect species currently found and described. The larva grows and eventually becomes a pupa, a stage marked by reduced movement and often sealed within a cocoon. Many of the early groups became extinct during the Permian-Triassic extinction event, the largest mass extinction in the history of the Earth, around 252 million years ago. [126], A large number of insects live either part or the whole of their lives underwater. Recently insects have also gained attention as potential sources of drugs and other medicinal substances. The tough and flexible endocuticle is built from numerous layers of fibrous chitin and proteins, criss-crossing each other in a sandwich pattern, while the exocuticle is rigid and hardened. Other insects produced by parthenogenesis are bees, wasps and ants, in which they spawn males. [113], In addition to the use of sound for communication, a wide range of insects have evolved chemical means for communication. [32], The internal phylogeny is based on the works of Sroka, Staniczek & Bechly 2014,[33] Prokop et al.
[75] Diffusive ventilation is simply a form of continuous gas exchange that occurs by diffusion rather than physically taking in the oxygen. Or what animal has the strongest bite? This helps to spread the plants, which increases plant diversity. Some insects, like wasps, bees, butterflies and ants, pollinate flowering plants. Insects are the only invertebrates to have developed active flight capability, and this has played an important role in their success. [146]:240243 Another solution, as shown in Delaware, has been to raise native plants to help support native pollinators like L. This is because inside the chorion two additional membranes develop from embryonic tissue, the amnion and the serosa. The meso- and metathoracic segments may each have a pair of wings, depending on the insect. Much of the scientific knowledge of genetics has been gained from fruit fly experiments and of population biology from flour beetle studies. Ventral sclerites are sometimes called laterosternites. The orders that contain the greatest numbers of species are Coleoptera (beetles), Lepidoptera (butterflies and moths), Hymenoptera (ants, bees, wasps), and Diptera (true flies). [17] However, modern phylogenetic studies have shown that "Apterygota" is not monophyletic,[18] and so does not form a good taxon. Some extinct insects had an additional pair of winglets attaching to the first segment of the thorax, for a total of three pairs. [a] The term is also occasionally extended to colloquial names for freshwater or marine crustaceans (e.g. Immature insects that go through incomplete metamorphosis are called nymphs or in the case of dragonflies and damselflies, also naiads. For instance, some nocturnal moths can perceive the ultrasonic emissions of bats, which helps them avoid predation.
[145] A serious environmental problem is the decline of populations of pollinator insects, and a number of species of insects are now cultured primarily for pollination management in order to have sufficient pollinators in the field, orchard or greenhouse at bloom time.
As insects get larger, this type of oxygen transport is less efficient and thus the heaviest insect currently weighs less than 100g. However, with increased atmospheric oxygen levels, as were present in the late Paleozoic, larger insects were possible, such as dragonflies with wingspans of more than two feet (60cm).
Ultrasonic recording and high-speed infrared videography of bat-moth interactions suggest the palatable tiger moth really does defend against attacking big brown bats using ultrasonic clicks that jam bat sonar.[105]. Some species are parasitic, and may vector diseases. Products made by insects. The eggs of ovoviviparous animals develop entirely inside the female, and then hatch immediately upon being laid. Translations of Aristotle's term also form the usual word for insect in Welsh (trychfil, from trychu "to cut" and mil, "animal"), Serbo-Croatian (zareznik, from rezati, "to cut"), Russian ( [nasekomoje], from se'/-sekat, "to cut"), etc. Envaginations at the anterior end of the hindgut form the Malpighian tubules, which form the main excretory system of insects.
Ants also help control animal populations by consuming small vertebrates. Insect flight has been a topic of great interest in aerodynamics due partly to the inability of steady-state theories to explain the lift generated by the tiny wings of insects. Insects are the only invertebrates to have evolved flight, and all flying insects derive from one common ancestor. Many insects are considered pests by humans.
[36]:2224 The exocuticle is greatly reduced in many insects during their larval stages, e.g., caterpillars. Pheromones, a type of semiochemical, are used for attracting mates of the opposite sex, for aggregating conspecific individuals of both sexes, for deterring other individuals from approaching, to mark a trail, and to trigger aggression in nearby individuals. [117] A few insects seasonally migrate large distances between different geographic regions (e.g., the overwintering areas of the monarch butterfly). Of all the insect orders, Orthoptera displays the most features found in other insects, including the sutures and sclerites. In Mesopotamian literature, the epic poem of Gilgamesh has allusions to Odonata that signify the impossibility of immortality. Silkworms produce silk and honey bees produce honey and both have been domesticated by humans. [8][9] Human activities also have effects on insect biodiversity. Color vision has been demonstrated in many species and phylogenetic analysis suggests that UV-green-blue trichromacy existed from at least the Devonian period between 416 and 359 million years ago. [141][142], Despite the large amount of effort focused at controlling insects, human attempts to kill pests with insecticides can backfire.
The eyes may include simple eyes or ocelli as well as compound eyes of varying sizes. This page was last edited on 13 July 2022, at 09:41. There are three types of pupae: obtect, exarate or coarctate. It was found that 70% of the fly genome is similar to the human genome, supporting the evolution theory.[155]. These insects are known to spread diseases such as malaria and yellow fever and because of such, mosquitoes indirectly cause more deaths of humans than any other animal. However, upon closer examination, their features differ significantly; most noticeably, they do not have the six-legged characteristic of adult insects. Spiracles are located in the pleural area.
Hearing has evolved independently at least 19 times in different insect groups. 
A portion of the vas deferens is often enlarged to form the seminal vesicle, which stores the sperm before they are discharged into the female.
Hemolymph pressure may be increased by muscle contractions or by swallowing air into the digestive system to aid in molting. Such insects often advertise their toxicity using warning colors. Some insects damage crops by feeding on sap, leaves, fruits, or wood. [36]:7077 The salivary glands (element 30 in numbered diagram) in an insect's mouth produce saliva. Allomones benefit their producer by the effect they have upon the receiver. Another simple form of parental care is to construct a nest (a burrow or an actual construction, either of which may be simple or complex), store provisions in it, and lay an egg upon those provisions. [132]:3 Insects play one of the most important roles in their ecosystems, which includes many roles, such as soil turning and aeration, dung burial, pest control, pollination and wildlife nutrition. Other theories are based on a pleural origin. The head capsule is made up of six fused segments, each with either a pair of ganglia, or a cluster of nerve cells outside of the brain. Some species, such as water striders, are capable of walking on the surface of water.
Insects can communicate with each other in a variety of ways. Their blood is not totally contained in vessels; some circulates in an open cavity known as the haemocoel. [107] Insects cannot effectively produce low-frequency sounds, and high-frequency sounds tend to disperse more in a dense environment (such as foliage), so insects living in such environments communicate primarily using substrate-borne vibrations. [124] Radar can also be deliberately used to monitor insects.[125]. The Zygentoma themselves possibly are not monophyletic, with the family Lepidotrichidae being a sister group to the Dicondylia (Pterygota and the remaining Zygentoma). [130][131], Insect ecology is the scientific study of how insects, individually or as a community, interact with the surrounding environment or ecosystem. Insect growth is constrained by the inelastic exoskeleton and development involves a series of molts. Mosquitoes have been found to hear up to 2kHz, and some grasshoppers can hear up to 50kHz. As insects gather nectar from different plants of the same species, they also spread pollen from plants on which they have previously fed. The ejaculatory duct is derived from an invagination of the epidermal cells during development and, as a result, has a cuticular lining. [160][161], Many species of insects are sold and kept as pets. Coarctate pupae develop inside the larval skin. But insect wings are in motion, with flapping and vibrations, resulting in churning and eddies, and the misconception that physics says "bumblebees can't fly" persisted throughout most of the twentieth century. These wagging movements can signal the arrival of new material into the nest and aggression between workers can be used to stimulate others to increase foraging expeditions. [30] However, other analyses have disputed this placement, finding it to be more likely a myriapod. In some of these species, sculpturing or various colored scales or hairs cause the beetle to resemble bird dung or other inedible objects. taste or smell) to a chemical stimulus where the chemicals act as signals to regulate the state or activity of a cell. Many species have acute vision capable of detecting minute movements.
The mixture of saliva and food then travels through the salivary tubes into the mouth, where it begins to break down.
Among the Aborigines of Australia of the Arrernte language groups, honey ants and witchetty grubs served as personal clan totems. [55] The ecologist Manu Sanders notes that the 2019 review was biased by mostly excluding data showing increases or stability in insect population, with the studies limited to specific geographic areas and specific groups of species. This ultimately affects humans since ensuring healthy crops is critical to agriculture. Holometabolism, or complete metamorphosis, is where the insect changes in four stages, an egg or embryo, a larva, a pupa and the adult or imago. Some insects display a rudimentary sense of numbers,[94] such as the solitary wasps that prey upon a single species. Updates?
Insects are distinguished from other arthropods by their body, which is divided into three major regions: (1) the head, which bears the mouthparts, eyes, and a pair of antennae, (2) the three-segmented thorax, which usually has three pairs of legs (hence Hexapoda) in adults and usually one or two pairs of wings, and (3) the many-segmented abdomen, which contains the digestive, excretory, and reproductive organs. ", "Evolutionary Biology of Insect Learning", "General Entomology Digestive and Excritory system", "On the morphology of the digestive system of two Monomorium ant species", "General Entomology Digestive and Excretory system", "The extraembryonic serosa protects the insect egg against desiccation", "Glossary of Lepidopteran and Odonate anatomy".
