Insect
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NawlinWiki
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Changed protection level for "[[Insect]]": no reason to move this page w/o discussion [edit=autoconfirmed:move=sysop]
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{{Taxobox
| name = Insects
| fossil_range = Early [[Devonian]]<ref name=EngelGrim/> (but see text) - Recent
| image = European honey bee extracts nectar.jpg
| image_caption = [[Western honey bee]] (Order [[Hymenoptera]])
| regnum = [[Animal]]ia
| phylum = [[Arthropod]]a
| subphylum = [[Hexapoda]]
| classis = '''Insecta'''
| classis_authority = [[Carolus Linnaeus|Linnaeus]], [[Systema Naturae|1758]]
| subdivision_ranks = Orders
| subdivision =
}}
[[Image:robal.png|right|300px|thumb|Insect anatomy <br>
'''A'''- Head '''B'''- Thorax '''C'''- Abdomen <br />
<div style="-moz-column-count:2; column-count:2;">
1. [[Antenna (biology)|antenna]]<br />
2. [[Ocellus|ocelli]] (lower)<br />
3. ocelli (upper)<br />
4. [[compound eye]]<br />
5. brain (cerebral [[Ganglion|ganglia]])<br />
6. [[prothorax]]<br />
7. dorsal blood vessel<br />
8. [[invertebrate trachea|trachea]]l tubes (trunk with [[spiracle]])<br />
9. [[mesothorax]]<br />
10. [[metathorax]]<br />
11. [[insect wing|forewing]]<br />
12. [[insect wing|hindwing]]<br />
13. mid-gut (stomach)<br />
14. dorsal blood vessel ("aorta")<br />
15. ovary<br />
16. [[hind-gut]] (intestine, rectum & anus)<br />
17. anus<br />
18. oviduct<br />
19. nerve chord (abdominal ganglia)<br />
20. [[Malphigian tubule system|Malpighian tubes]]<br />
21. tarsal pads<br />
22. claws<br />
23. [[Arthropod leg|tarsus]]<br />
24. [[Arthropod leg|tibia]]<br />
25. [[Arthropod leg|femur]]<br />
26. [[Arthropod leg|trochanter]]<br />
27. fore-gut (crop, gizzard)<br />
28. thoracic ganglion<br />
29. [[Arthropod leg|coxa]]<br />
30. salivary gland<br />
31. [[subesophageal ganglion]]<br />
32. mouthparts<br />
</div>]]
'''Insects''' ([[Class (biology)|Class]] '''Insecta''') are a major group of [[arthropod]]s and the most diverse group of [[animal]]s on the Earth, with over a million described [[species]]—more than half of all known living organisms<ref name="Chapman">{{cite book |author=Chapman, A. D. |year=2006 |title=Numbers of living species in Australia and the World |pages=60pp |Publisher=Canberra: [[Australian Biological Resources Study]] |id=ISBN 978-0-642-56850-2 |url=http://www.deh.gov.au/biodiversity/abrs/publications/other/species-numbers/index.html}}</ref><ref>[http://www.globalchange.umich.edu/globalchange2/current/lectures/biodiversity/biodiversity.html Threats to Global Biodiversity] (Accessed December 2007</ref>—with estimates of undescribed species as high as 30 million, thus potentially representing over 90% of the differing life forms on the planet.<ref>{{cite journal|last=Erwin|first=Terry L.|year=1982|title=Tropical forests: their richness in Coleoptera and other arthropod species|journal=Coleopt. Bull.|volume=36|pages=74–75}}</ref> Insects may be found in nearly all environments on the planet, although only a small number of species occur in the [[ocean]]s, a habitat dominated by the other arthropod group of [[crustacean]]s.
There are approximately 5,000 [[Odonata|dragonfly]] species, 2,000 [[Mantodea|praying mantis]], 20,000 [[orthoptera|grasshopper]], 170,000 [[lepidoptera|butterfly and moth]], 120,000 [[Diptera|fly]], 82,000 [[hemiptera|true bug]], 360,000 [[beetle]], and 110,000 [[hymenoptera|bee, wasp and ant]] species described to date. Estimates of the total number of current species, including those not yet known to science, range from two million to fifty million, with newer studies favouring a lower figure of about six to ten million.<ref name="Chapman"/><ref>{{cite journal |quotes=no |author=Vojtech Novotny, Yves Basset, Scott E. Miller, George D. Weiblen, Birgitta Bremer, Lukas Cizek & Pavel Drozd |year=2002 |title=Low host specificity of herbivorous insects in a tropical forest |journal=[[Nature (journal)|Nature]] |volume=416 |pages=841–844 |doi=10.1038/416841a}}</ref><ref>{{cite book|author=Erwin, Terry L. |year=1997 |title=Biodiversity at its utmost: Tropical Forest Beetles |pages=27–40}} In: {{cite book |author=Reaka-Kudla, M. L., D. E. Wilson & E. O. Wilson (eds.) |title=Biodiversity II |publisher=Joseph Henry Press, Washington, D.C.}}</ref> Adult modern insects range in size from a 0.139 mm (0.00547 [[Inch|in]]) [[fairyfly]] (''[[Dicopomorpha echmepterygis]]'') to a 55.5 cm (21.9 in) long [[stick insect]] (''[[Phobaeticus serratipes]]'').<ref name="walker">Walker, T.J., ed. 2001. University of Florida Book of Insect Records, 2001. [http://ufbir.ifas.ufl.edu/]</ref> The heaviest documented insect was a [[Giant Weta]] of 70 [[gram|g]] (2½ [[Ounce|oz]]), but other possible candidates include the [[Goliath beetle]]s ''[[Goliathus goliatus]]'', ''[[Goliathus regius]]'' and [[Cerambycidae|Cerambycid]] beetles such as ''[[Titanus giganteus]]'', though no one is certain which is truly the heaviest.<ref name="walker"/>
The study of insects (from [[Latin]] ''insectus'', meaning "cut into sections") is called [[entomology]], from the [[Greek language|Greek]] εντομον, also meaning "cut into sections".<ref>{{Cite book |title=[[Oxford English Dictionary]] |publisher=Oxford University Press}}</ref>
==Body structure==
Insects possess segmented bodies supported by an [[exoskeleton]], a hard outer covering made mostly of [[chitin]]. The segments of the body are organized into three distinctive but interconnected units, or [[tagma (biology)|tagmata]]; a head, a [[thorax]], and an [[abdomen]]. The head supports a pair of sensory [[Antenna (biology)|antennae]], a pair of [[compound eye]]s, one to three simple eyes ("[[ocelli]]") and three sets of variously modified appendages that form the [[mouthparts]]. The thorax has [[6 (number)|six]] segmented [[arthropod leg|legs]] (one pair each for the prothorax, mesothorax and the metathorax segments making up the thorax) and two or four [[insect wing|wings]] (if present in the species). The abdomen (made up of eleven segments some of which may be reduced or fused) has most of the [[digestion|digestive]], [[Respiration (physiology)|respiratory]], [[Excretion|excretory]] and reproductive internal structures.
===Nervous system===
Their [[nervous system]] can be divided into a brain and a [[ventral nerve cord]]. The head capsule (made up of six fused segments) has six pairs of [[ganglion|ganglia]]. The first three pairs are fused into the brain, while the three following pairs are fused into a structure called the [[subesophageal ganglion]].
The thoracic segments have one ganglion on each side, which are connected into a pair, one pair per segment. This arrangement is also seen in the abdomen but only in the first eight segments. Many species of insects have reduced numbers of ganglia due to fusion or reduction. Some cockroaches have just six ganglia in the abdomen, whereas the wasp ''[[Vespa crabro]]'' has only two in the thorax and three in the abdomen. And some, like the house fly ''[[Musca domestica]]'', have all the body ganglia fused into a single large thoracic ganglion.
Until very recently, no one had ever documented the presence of [[nociceptor]]s (the cells that detect and transmit sensations of [[pain]]) in insects (e.g., <ref>C. H. Eisemann, W. K. Jorgensen, D. J. Merritt, M. J. Rice, B. W. Cribb, P. D. Webb and M. P. Zalucki (1984) Do insects feel pain? — A biological view. Cellular and Molecular Life Sciences 40: 1420-1423</ref>), though recent findings of nociception in larval [[Drosophila melanogaster|fruit flies]] challenges this<ref>Tracey, J., W. Daniel, R. I. Wilson, G. Laurent, and S. Benzer (2003) ''painless'', a ''Drosophila'' gene essential for nociception. Cell 113: 261-273. http://dx.doi.org/10.1016/S0092-8674(03)00272-1</ref> and raises the possibility that some insects may be capable of feeling pain.
===Respiration and circulation===
Insect respiration is accomplished without [[lung]]s, using a system of internal tubes and sacs through which gases either diffuse or are actively pumped, delivering oxygen directly to the adjoining body tissues (see [[Invertebrate trachea]]). Since oxygen is delivered directly, the circulatory system is not used to carry oxygen, and is therefore greatly reduced; it has no closed vessels (i.e., no [[vein]]s or [[artery|arteries]]), consisting of little more than a single, perforated dorsal tube which pulses [[peristalsis|peristaltically]], and in doing so helps circulate the [[hemolymph]] inside the body cavity. Air is taken in through [[spiracles]], openings on the sides of the abdomen.
===Exoskeleton===
Most higher insects have two pairs of [[Insect wing|wings]] located on the second and third thoracic segments. Insects are the only [[invertebrate]]s to have developed [[Insect flight|flight]], and this has played an important part in their success. The winged insects, and their wingless relatives, make up the subclass [[Pterygota]]. [[Insect flight]] is not very well understood, relying heavily on turbulent aerodynamic effects. The primitive insect groups use muscles that act directly on the wing structure. The more advanced groups making up the [[Neoptera]] have foldable wings and their muscles act on the thorax wall and power the wings indirectly. These muscles are able to contract multiple times for each single nerve impulse, allowing the wings to beat faster than would ordinarily be possible (''see [[insect flight]]'').
Their outer skeleton, the cuticle, is made up of two layers; the [[epicuticle]] which is a thin and waxy water resistant outer layer and contains no chitin, and another layer under it called the [[procuticle]]. This is chitinous and much thicker than the epicuticle and has two layers, the outer being the exocuticle while the inner is the endocuticle. The tough and flexible endocuticle is built from numerous layers of fibrous chitin and proteins, criss-crossing each others in a sandwich pattern, while the exocuticle is rigid and [[sclerotization|sclerotized]]. The exocuticle is greatly reduced in many soft-bodied insects, especially the [[larva]]l stages (e.g., [[caterpillar]]s).
==Development==
[[Image:Hoverflies mating midair.jpg|thumb|left|Hoverflies mating in flight]]
Most insects hatch from [[egg (biology)|eggs]], but some are [[Ovoviviparity|ovoviviparous]] or [[viviparous]], and all undergo a series of [[ecdysis|moults]] as they develop and grow in size. This manner of growth is necessitated by the inelastic exoskeleton. Moulting is a process by which the individual escapes the confines of the exoskeleton in order to increase in size, then grows a new and larger outer covering. In some insects, the young are called '''nymphs''' and are similar in form to the adult except that the wings are not developed until the adult stage. This is called ''incomplete [[metamorphosis (biology)|metamorphosis]]'' and insects showing this are termed ''[[Hemimetabolism|hemimetabolous]]''. ''[[Holometabolism|Holometabolous]]'' insects show ''complete metamorphosis'', which distinguishes the [[Endopterygota]] and includes many of the most successful insect groups. In these species, an egg hatches to produce a '''[[larva]]''', which is generally worm-like in form, and can be divided into five different forms; eruciform (caterpillar-like), scarabaeiform (grublike), campodeiform (elongated, flattened, and active), elateriform (wireworm-like) and vermiform (maggot-like). The larva grows and eventually becomes a '''[[pupa]]''', a stage marked by reduced movement and foten sealed within a [[pupa|cocoon]]. There are three types of pupae; obtect (the pupa is compact with the legs and other appendages enclosed), exarate (where the pupa has the legs and other appendages free and extended) and coarctate (where the pupa develops inside the larval skin). In the pupal stage, the insect undergoes considerable change in form to emerge as an adult, or '''[[imago]]'''. Butterflies are an example of an insect that undergoes complete metamorphosis. Some insects have even evolved [[hypermetamorphosis]].
Some insects (parastic wasps) show [[polyembryony]] where a single fertilized egg can divide into many and in some cases thousands of separate embryos. Other developmental and reproductive variations include [[haplodiploidy]], [[Polymorphism (biology)|polymorphism]], [[paedomorphosis]] (metathetely and prothetely), [[sexual dimorphism]], [[parthenogenesis]] and more rarely [[hermaphroditism]].
==Senses and communication==
[[Image:Common brown robberfly with prey.jpg|thumb|A [[robberfly]] with its prey, a [[hoverfly]]]]
Many insects possess very sensitive and/or specialized organs of [[sense|perception]]. Some insects such as bees can perceive [[ultraviolet]] wavelengths, or detect [[polarized light]], while the [[antenna (biology)|antennae]] of male moths can detect the [[pheromone]]s of female moths over distances of many kilometres. There is a pronounced tendency for there to be a trade-off between visual acuity and chemical or tactile acuity, such that most insects with well-developed eyes have reduced or simple antennae, and vice-versa. There are a variety of different mechanisms by which insects perceive sound, and it is by no means universal; the general pattern, however, is that if an insect can produce sound, then it can also hear sound, though the range of frequencies they can hear is often quite narrow (and may in fact be limited to only the frequency that they themselves produce). Some nocturnal moths can perceive the [[ultrasonic]] emissions of [[bat]]s, a mechanism which helps them avoid predation. Certain predatory and parasitic insects can detect the characteristic sounds made by their prey/hosts. Bloodsucking insects have special sensory structures that can detect [[infrared]] emissions, and use them to home in on their hosts.
[[Image:SensillaeImms.png|thumb|Sensillae: sensory structures on insects]]
A few such insects also have a well-developed number sense,{{Fact|date=April 2008}} among the solitary wasps that provision with a single species of prey. The mother wasp lays her eggs in individual cells and provides each egg with a number of live caterpillars on which the young feed when hatched. Some species of wasp always provide five, others twelve, and others as high as twenty-four caterpillars per cell. The number of caterpillars is different among species, but it is always the same for each sex of larvae. The male solitary wasp in the genus ''[[Eumenes (genus)|Eumenes]]'' is smaller than the female, so the mother of one species supplies him with only five caterpillars; the larger female receives ten caterpillars in her cell. She can in other words distinguish between both the numbers five and ten in the caterpillars she is providing and which cell contains a male or a female.
===Light production and vision===
A few insects, such as members of the families Poduridae and Onychiuridae (Collembola), [[Mycetophilidae]] (Diptera), and the beetle families [[Lampyridae]], [[Phengodidae]], [[Elateridae]] and [[Staphylinidae]] are [[bioluminescent]]. The most familiar group are the fireflies, beetles of the family Lampyridae. Some species are able to control this light generation to produce flashes. The function varies with some species using them to attract mates, while others use them to lure prey. Cave dwelling larvae of ''[[Arachnocampa]]'' (Mycetophilidae, Fungus gnats) glow to lure small flying insects into sticky strands of silk.<ref>{{cite journal|title=Literature review of the New Zealand glowworm ''Arachnocampa luminosa'' (Diptera: Keroplatidae) and related cave-dwelling Diptera|last=Pugsley|first=Chris W.|journal=New Zealand Entomologist|year=1983|volume=7|issue=4|pages=419–424|url=http://www.ento.org.nz/nzentomologist/free_issues/NZEnto07_4_1983/Volume%207-4-419-424.pdf}}</ref>
Some fireflies of the genus ''[[Photuris]]'' [[mimicry|mimic]] the flashing of female ''[[Photinus]]'' species to attract males of that species, which are then capture and devoured.<ref>{{cite journal|title=Occurrence of Aggressive Mimicry in Fireflies|first=James E.|last=Lloyd|journal=The Florida Entomologist|volume=67|issue=3|year=1984|pages=368–376|doi=10.2307/3494715 }}</ref> The colours of emitted light vary from dull blue (''Orfelia fultoni'', Mycetophilidae) to the familiar greens and the rare reds (''Phrixothrix tiemanni'', Phengodidae).<ref>{{cite book|first=James E.|last=Lloyd|coauthors=Erin C. Gentry|title=Bioluminescence|pages=115-120|title=in
Resh, V.H. and R.C. Cardé (editors) 2003. The Encyclopedia of Insects|publisher=Academic Press}}</ref>
Most insects except some species of cave dwelling crickets are able to perceive light and dark. Many species have acute vision capable of detecting minute movements. The eyes include simple eyes or [[Ocellus|ocelli]] as well as [[compound eye]]s of varying sizes. Many species are able to detect light in the infrared, ultraviolet as well as the visible light wavelengths. Colour vision has been demonstrated in many species.
[[Image:Bottle-fly.JPG|thumb|left|Bottle flies are considered "pests"]]
===Sound production and hearing===
Insects were the earliest organisms to produce sounds and to sense them. Soundmaking in insects is achieved mostly by mechanical action of appendages. In the [[grasshopper]]s and crickets this is achieved by [[stridulation]]. The [[cicada]]s have the loudest sounds among the insects and have special modifications to their body and musculature to produce and amplify sounds. Some species such as the African [[cicada]], ''[[Brevisana brevis]]'' have been measured at 106.7 [[decibel]]s at a distance of 50 cm (20 in).<ref name="walker"/> Some insects, such as the [[hawk moth]]s and [[Hedylidae|Hedylid]] butterflies, can hear ultrasound and take evasive action when they sense detection by bats. Some moths produce ultrasound clicks and these were earlier thought to have a role in jamming the bat echolocation, but it was subsequently found that these are produced mostly by unpalatable moths to warn bats, just as [[Aposematism|warning colouration]]s are used against predators that hunt by sight.<ref>{{cite journal|last=Hristov|first=N.I.|coauthors=Conner, W.E.|year=2005|title=Sound strategy: acoustic aposematism in the bat–tiger moth arms race|journal=Naturwissenschaften|volume=92|pages=164–169|doi=10.1007/s00114-005-0611-7}}</ref> These calls are also made by other moths involved in [[mimicry]].<ref>{{cite journal|last=Barber|first=J. R.|coauthors=W. E. Conner|year=2007|title=Acoustic mimicry in a predator–prey interaction|journal=Proc. Nat. Acad. Sci.|volume=104|issue=22|pages=9331–9334|url=http://www.pnas.org/cgi/content/figsonly/104/22/9331|doi=10.1073/pnas.0703627104|pmid=17517637}}</ref>
Very low sounds are also produced in various species of Neuroptera, [[Lepidoptera]] ([[butterflies]] and [[moths]]), [[Coleoptera]] and [[Hymenoptera]] produced by the mechanical actions of movement often aided by special microscopic stridulatory structures.
Most sound-making insects also have [[tympanal organ]]s that can perceive airborne sounds. Most insects are also able to sense vibrations transmitted by the substrate. Communication using substrate-borne [[vibration]]al signals is more widespread among insects because of the size constraints in producing air-borne sounds.<ref>{{cite journal|last=Virant-Doberlet|first=M.|coauthors=Čokl A.|year=2004|title=Vibrational communication in insects|journal=Neotropical Entomology|volume=33|issue=2|pages=121–134|url=http://www.scielo.br/pdf/ne/v33n2/a01v33n2.pdf|doi=10.1590/S1519-566X2004000200001}}</ref> 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.<ref>{{cite journal|last=Bennet-Clark|first=H.C.|year=1998|title=Size and scale effects as constraints in insect sound communication|journal=Phil. Trans. R. Soc. Lond. B|volume=353|pages=407–419|doi=10.1098/rstb.1998.0219}}</ref> The mechanisms of production of vibrational signals are just as diverse as those for producing sound in insects.
Some species use vibrations for communicating within members of the same species, such as to attract mates as in the songs of the [[shield bug]] ''[[Nezara viridula]]''<ref>{{cite journal|journal=Journal of Insect Behavior|title=The Influence of Substrate on Male Responsiveness to the Female Calling Song in ''Nezara viridula''|volume=14|issue=3|pages=313–332|year=2001|first=Nadège|last=Miklas|coauthors=Nataša Stritih,Andrej Čokl, Meta Virant-Doberlet, Michel Renou|doi=10.1023/A:1011115111592}}</ref> while it can also be used to communicate between entirely different species, such as between ants and myrmecophilous lycaenid caterpillars.<ref>{{cite journal|last=DeVries|first=P. J.|year=1990|title=Enhancement of symbiosis between butterfly caterpillars and ants by vibrational communication|journal=Science|volume=248|pages=1104–1106|doi=10.1126/science.248.4959.1104|pmid=17733373}}</ref>
The [[Madagascar hissing cockroach]] has the ability to press air through the spiracles to make a hissing noise, and the [[Death's-head Hawkmoth]] makes a squeaking noise by forcing air out of their [[pharynx]].
===Chemical communication===
In addition to the use of sound for communication, a wide range of insects have evolved chemical means for communication. These chemicals, termed [[semiochemical]]s, are often derived from plant metabolites include those meant to attract, repel and provide other kinds of information. While some chemicals are targeted at individuals of the same species, others are used for communication across species. The use of scents is especially well known to have developed in social insects.
==Social behaviour==
[[Image:Termite Cathedral DSC03570.jpg|thumb|right|A termite mound made by the cathedral termite]]
[[Social insect]]s, such as the [[termite]]s, [[ant]]s and many [[bee]]s and [[wasp]]s, are the most familiar species of [[Eusociality|eusocial]] animal. They live together in large well-organized colonies that may be so tightly integrated and genetically similar that the colonies of some species are sometimes considered [[superorganism]]s. It is sometimes argued that the various species of [[honey bee]] are the only invertebrates (and indeed one of the few non-human groups) to have evolved a system of abstract symbolic communication (i.e., where a behaviour is used to ''represent'' and convey specific information about something in the environment), called the "[[Bee learning and communication|dance language]]" - the angle at which a bee dances represents a direction relative to the sun, and the length of the dance represents the distance to be flown.
Only those insects which live in nests or colonies demonstrate any true capacity for fine-scale spatial orientation or "homing" - this can be quite sophisticated, however, and allow an insect to return unerringly to a single hole a few millimetres in diameter among a mass of thousands of apparently identical holes all clustered together, after a trip of up to several kilometres' distance, and (in cases where an insect [[hibernation|hibernates]]) as long as a year after last viewing the area (a phenomenon known as [[philopatry]]). A few insects [[Insect migration|migrate]], but this is a larger-scale form of [[navigation]], and often involves only large, general regions (e.g., the overwintering areas of the [[Monarch butterfly]]).
===Care of young===
Most insects lead short lives as adults, and rarely interact with one another except to mate, or compete for mates. A small number exhibit some form of [[parental care]], where they will at least guard their eggs, and sometimes continue guarding their offspring until adulthood, and possibly even actively feeding them. 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. The adult does not contact the growing offspring, but it nonetheless does provide food. This sort of care is typical of bees and various types of wasps.
==Locomotion==
===Flight===
{{main|Insect flight}}
Insects are the only group of invertebrates to have developed flight. The evolution of insect wings has been a subject of debate. Some proponents suggest that the wings are para-notal in origin while others have suggested they are modified gills. In the Carboniferous age, some of the ''Meganeura'' dragonflies had as much as a 50 cm (20 in) wide wingspan. The appearance of gigantic insects has been found to be consistent with high atmospheric oxygen. The percentage of oxygen in the atmosphere found from ice core-samples was as high as 35% compared to the current 21%. The respiratory system of insects constrains their size, however the high oxygen in the atmosphere allowed larger sizes.<ref>{{cite journal|last=Dudley|first=R.|year=1998|title= Atmospheric oxygen, giant Paleozoic insects and the evolution of aerial locomotor performance|journal=Journal of Experimental Biology|volume=201|issue=8|pages=1043–1050|url=http://jeb.biologists.org/cgi/reprint/201/8/1043.pdf}}</ref> The largest flying insects today are much smaller and include several moth species such as the [[Atlas moth]] and the White Witch (''[[Thysania agrippina]]'').
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.
In addition to powered flight, many of the smaller insects are also dispersed by winds. These include the [[aphid]]s which are often transported long distances by low-level jet streams.<ref>{{cite journal|last=Drake|first=V. A.|coauthors=R. A. Farrow|year=1988|title=The Influence of Atmospheric Structure and Motions on Insect Migration|journal=Annual Review of Entomology|volume=33|pages=183–210|doi=10.1146/annurev.en.33.010188.001151}}</ref>
===Walking===
Many adult insects use six legs for walking and have adopted a [[tripedal]] [[gait]]. The tripedal gait allows for rapid walking whilst always having a stable stance and has been studied extensively in [[cockroach]]es. The legs are used in alternate triangles touching the ground. 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, whilst the front and rear right leg and the middle left leg are lifted and moved forward to a new position. When they touch the ground to form a new stable triangle the other legs can be lifted and brought forward in turn and so on.
The purest form of the tripedal gait is seen in insects moving at speed. However, this type of locomotion is not rigid and insects can adapt a variety of gaits; for example, when moving slowly, turning, or avoiding obstacles, four or more feet may be touching the ground. Insects can also adapt their gait to cope with the loss of one or more limbs.
[[Cockroach]]es are amongst the fastest insect runners and at full speed actually adopt a bipedal run to reach a high velocity in proportion to their body size. As [[Cockroach]]es move extremely rapidly, they need recording at several hundred frames per second to reveal their gait. More sedate locomotion is also studied by scientists in stick insects [[Phasmatodea]].
A few insects have evolved to walk on the surface of the water, especially the bugs of the family, [[Water strider|Gerridae]], also known as water striders. 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.
Insect walking is of particular interest as an alternative form of locomotion to the use of wheels for robots ([[Robot locomotion]]).
===Swimming===
[[Image:Notonecta glauca01.jpg|thumb|right|The backswimmer ''[[Notonecta glauca]]'' underwater, showing the paddle like hindleg adaptation]]
A large number of insects live either parts or the whole of their lives underwater. In many of the more primitive orders the immature stages are aquatic while some other groups have aquatic adults as well.<ref name=aquins>{{cite book|author=Richard W. Merritt, Kenneth W. Cummins, and Martin B. Berg (editors)|year=2007|title=An Introduction to the Aquatic Insects of North America|publisher=Kendall Hunt Publishers|isbn=9780757550492|edition=4th Edition}}</ref>
Many of these species have adaptations to help in locomotion under water. The water beetles and water bugs have legs adapted into paddle like structures. Dragonfly naiads, use jet propulsion, forcibly expelling water out of the rectal chamber.<ref>{{cite journal|last=Mill|first=P. J.|coauthors=R. S. Pickard|year=1975|title=Jet-propulsion in anisopteran dragonfly larvae|journal=Journal of Comparative Physiology A: Neuroethology, Sensory, Neural, and Behavioral Physiology|volume=97|issue=4|pages=329–338|doi=10.1007/BF00631969}}</ref>
Some species like the [[water strider]]s are capable of walking on the surface of water. They can do this because their claws are not at the tips of the legs as in most insects, but recessed in a special groove further up the leg; this prevents the claws from piercing the water's surface film.<ref name=aquins /> Other insects such as the [[staphylinidae|Rove beetle]] ''[[Stenus]]'' are known to emit salivary secretions that reduce surface tension making it possible for them to move on the surface of water by [[Marangoni effect|Marangoni propulsion]] (also known by the German term ''Entspannungsschwimmen'').<ref>{{cite journal|last=Linsenmair|first=K.|coauthors=Jander R.|year=1976|title=Das "entspannungsschwimmen" von ''Velia'' and ''Stenus''|journal=Naturwissenschaften|volume=50|pages=231|doi=10.1007/BF00639292}}</ref><ref>{{cite journal|last=Bush|first=J. W. M.|coauthors=David L. Hu|year=2006|title=Walking on Water: Biolocomotion at the Interface|journal=Annu. Rev. Fluid Mech.|volume=38|pages=339–369|url=http://www.cims.nyu.edu/~dhu/Pubweb/Bush_Hu_06.pdf|doi=10.1146/annurev.fluid.38.050304.092157}}</ref>
Species that are submerged also have adaptations to aid in respiration. Many larval forms have gills that can extract oxygen dissolved in water, while others need to rise to the water surface to replenish air supplies which may be held or trapped in special structures.<ref name=aquins />
==Evolution==
<!--[[Image:Insect antennae comparison.jpg|thumb|right|Evolution has produced astonishing variety in insects. Pictured are some of the possible shapes of [[Antenna (biology)|antennae]].]] This image is currently taking too much real estate -->
{{Main|Insect evolution}}
The relationships of insects to other animal groups remain unclear. Although more traditionally grouped with millipedes and centipedes, evidence has emerged favoring closer [[evolution]]ary ties with the crustaceans. In the [[Pancrustacea]] theory insects, together with [[Remipedia]] and [[Malacostraca]], make up a natural [[clade]].
Other terrestrial arthropods, such as [[centipede]]s, [[millipede]]s, [[scorpion]]s and [[spider]]s, are sometimes confused with insects since their body plans can appear similar, sharing (as do all arthropods) a jointed exoskeleton. However upon closer examination their features differ significantly; most noticeably they do not have the six legs characteristic of adult insects.
The higher level phylogeny of the arthropods continues to be a matter of debate and research.
{{userboxtop|toptext= }}
{{clade| style=font-size:75%;line-height:75%
|1={{clade
|1={{clade
|1=[[Hexapoda]] ([[Insect|Insecta]], [[collembola]], [[diplura]], [[protura]])
|2=[[Crustacea]] ([[crab]]s, [[shrimp]], [[isopod]]s)
}}
|label2=[[Myriapoda]]
|2={{clade
|1=[[Pauropoda]]
|2=[[Diplopoda]] (Millipedes)
|3=[[Chilopoda]] (Centipedes)
|4=[[Symphyla]]
}}
|label3=[[Chelicerata]]
|3={{clade
|1=[[Arachnida]] ([[Spider]]s, [[scorpion]]s and allies)
|2=[[Eurypterida]] (Sea scorpions: Extinct)
|3=[[Xiphosura]] (Horseshoe crabs)
|4=[[Pycnogonida]] (Sea spiders)
}}
|4=[[Trilobites]] (Extinct)
}}
}}
A [[phylogenetic]] tree of the arthropods and related groups.<ref>Tree of Life Web Project. 1995. Arthropoda. Version 01 January 1995 (temporary). [http://www.tolweb.org/Arthropoda] in The Tree of Life Web Project, [http://tolweb.org/]</ref>
{{userboxbottom}}
The oldest definitive insect fossil is the [[Devonian]] ''Rhyniognatha hirsti'', from the 396 million year old<ref>{{cite journal|author=Rice, C. M., Ashcroft, W. A., Batten, D. J., Boyce, A. J., Caulfield, J. B. D., Fallick, A. E., Hole, M. J., Jones, E., Pearson, M. J., Rogers, G., Saxton, J. M., Stuart, F. M., Trewin, N. H. & Turner, G.|year=1995|title=A Devonian auriferous hot spring system, Rhynie, Scotland|journal=Journal of the Geological Society, London|volume=152|pages=229–250|doi=10.1144/gsjgs.152.2.0229}}</ref> [[Rhynie chert]]. This species already possessed dicondylic mandibles, a feature associated with winged insects, suggesting that wings may already have evolved at this time. Thus, the first insects probably appeared earlier, in the [[Silurian]] period.<ref name="EngelGrim">{{cite journal|url=http://www.nature.com/nature/journal/v427/n6975/full/nature02291.html|last=Engel|first=Michael S. |coauthors=David A. Grimaldi|year=2004|title=New light shed on the oldest insect|journal=Nature|volume=427|pages=627–630|doi=10.1038/nature02291}}</ref>
The origins of [[insect flight]] remain obscure, since the earliest winged insects currently known appear to have been capable fliers. Some extinct insects had an additional pair of winglets attaching to the first segment of the thorax, for a total of three pairs. So far, there is nothing that suggests that the insects were a particularly successful group of animals before they got their wings.
[[Pennsylvanian|Late Carboniferous]] and [[Cisuralian|Early Permian]] insect orders include both several current very long-lived groups and a number of Paleozoic forms. During this era, some giant dragonfly-like forms reached wingspans of 55 to 70 cm, (22-28 in) making them far larger than any living insect. This gigantism may have been due to higher atmospheric oxygen levels that allowed increased respiratory efficiency relative to today. The lack of flying vertebrates could have been another factor.
Most extant orders of insects developed during the [[Permian]] era that began around 270 million years ago. 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.
The remarkably successful Hymenopterans appeared in the [[Cretaceous]] but achieved their diversity more recently, in the [[Cenozoic]]. A number of highly-successful insect groups evolved in conjunction with [[flowering plants]], a powerful illustration of [[co-evolution]].
Many modern insect genera developed during the [[Cenozoic]]; insects from this period on are often found preserved in [[amber]], often in perfect condition. Such specimens are easily compared with modern species. The study of fossilized insects is called [[paleoentomology]].
===Coevolution===
:{{seealso|Coevolution}}
Insects were among the earliest terrestrial herbivores and acted as major selection agents on plants. Plants evolved chemical [[Plant defense against herbivory|defenses against this herbivory]] and the insects in turn evolved mechanisms to deal with plant toxins. Many insects make use of these toxins to protect themselves from their predators. And such insects advertise their toxicity using warning colours. This successful evolutionary pattern has also been utilized by [[mimic]]s. Over time, this has led to complex groups of [[coevolution|co-evolved]] species. Conversely, some interactions between plants and insects are beneficial (''see'' [[pollination]]), and coevolution has led to the development of very specific [[mutualism]]s in such systems.
==Classification==
Traditional morphology-based systematics has included in the [[subphylum]] [[Hexapoda]] four groups - Insects ([[Ectognatha]]), springtails ([[Collembola]]), [[Protura]] and [[Diplura]], the latter three being grouped together as [[Entognatha]] on the basis of internalized mouthparts. Supraordinal relationships have undergone numerous changes with the advent of [[cladistic]] methods and genetic data. A recent hypothesis is that Hexapoda is polyphyletic, with the entognath classes having separate evolutionary histories from Insecta.
As many of the traditional morphology-based taxa have been shown to be paraphyletic, it is best to avoid using terms such as [[subclass]], [[superorder]] and [[infraorder]] and instead focus on monophyletic groupings. The following list represents the best supported monophyletic groupings for the Insecta.
{{userboxtop|toptext= }}
{{Clade | style=font-size:75%;line-height:75%
| label1=[[Insecta]]
| 1={{Clade
| label1=[[Monocondylia]]
| label2=[[Dicondylia]]
| 1=[[Archaeognatha]]
| 2={{Clade
| 1=[[Thysanura]]
| label2=[[Pterygota]]
| 2={{Clade
| label1=[[Paleoptera]]
| 1={{Clade
|1=[[Ephemeroptera]]
|2=[[Odonata]]
}}
| label2=[[Neoptera]]
| 2={{Clade
| label1=
| 1=[[Plecoptera]]
| 2=[[Embiidina]]
| 3=[[Phasmida]]
| 4=[[Orthoptera]]
| 5=[[Mantophasmatodea]]
| 6=[[Zoraptera]]
| 7=[[Dictyoptera]]
| 8=[[Dermaptera]]
| 9=[[Grylloblattodea]]
| 10={{Clade
| 1=[[Psocodea]]
| 2=[[Thysanoptera]]
| 3=[[Hemiptera]]
| 4=[[Endopterygota]]
}} }} }} }} }} }}
<small>Simplified [[Cladogram]] of insect groups<ref>[http://www.tolweb.org/Insecta/8205 Tree of Life, Insecta]</ref> and very simplified. Note that [[Apterygota]], [[Palaeoptera]] and [[Exopterygota]] are possibly [[paraphyletic]] groups.</small>
{{userboxbottom}}
† signifies an extinct taxon.
'''[[Apterygota]]'''
* [[Monura]] †
'''[[Monocondylia]]'''
* [[Archaeognatha]]=Microcoryphia (bristletails)
'''[[Dicondylia]]'''
:* [[Thysanura]]=Zygentoma (silverfish)
:'''[[Pterygota]]'''
:: '''[[Paleoptera]]'''
::* [[Ephemeroptera]] (mayflies)
::* [[Palaeodictyoptera]] †
::* [[Megasecoptera]] †
::* [[Archodonata]] †
::* [[Diaphanopterodea]] †
::* [[Protodonata]]=Meganisoptera †
::* [[Protanisoptera]] †
::* [[Triadophlebioptera]] †
::* [[Protozygoptera]]=Archizygoptera †
::* [[Odonata]] (dragonflies, damselflies)
[[Image:Aust blue dragonfly02.jpg|thumb|''[[Orthetrum caledonicum]]'', the Blue Skimmer dragonfly]]
:: '''[[Neoptera]]'''
::: '''[[Polyneoptera]]'''
:::* [[Caloneurodea]] †
:::* [[Titanoptera]] †
:::* [[Protorthoptera]] †
:::* [[Plecoptera]] (stoneflies)
:::* [[Embiidina]]=Embioptera (webspinners)
:::* [[Zoraptera]] (angel insects)
:::* [[Dermaptera]] (earwigs)
:::* [[Orthoptera]] (grasshoppers, crickets, katydids)
:::* [[Phasmatodea]] (stick insects)
:::* [[Notoptera]] (ice-crawlers & gladiators)
:::* [[Blattaria]] (cockroaches)
::::* [[Isoptera]] (termites - included in Blattaria)
:::* [[Mantodea]] (mantids)
[[Image:Zorak-Mantis.png|thumb|A [[Chinese Mantis]].]]
::: '''[[Paraneoptera]]'''
:::* [[Psocodea]] (booklice, barklice)
::::* [[Mallophaga]] (chewing lice - in Psocodea)
::::* [[Anoplura]] (sucking lice - in Psocodea)
:::* [[Thysanoptera]] (thrips)
:::* [[Hemiptera]] (true bugs, aphids, cicadas)
[[Image:European wasp white bg.jpg|thumb|A [[Yellowjacket]] wasp.]]
::: '''[[Endopterygota]]'''=Holometabola
:::* [[Glosselytrodea]] †
:::* [[Miomoptera]] †
:::* [[Hymenoptera]] (wasps, bees, ants)
:::* [[beetle|Coleoptera]] (beetles)
:::* [[Strepsiptera]] (twisted-winged parasites)
::: [[Neuropterida]]
:::* [[Raphidioptera]] (snakeflies)
:::* [[Megaloptera]] (alderflies, dobsonflies)
:::* [[Neuroptera]] (lacewings, antlions)
::: [[Antliophora]]/[[Mecopteroidea]]
:::* [[Mecoptera]] (scorpionflies, hangingflies)
::::* [[Siphonaptera]] (fleas - in Mecoptera)
[[Image:Syrphid fly on Grape hyacinth.jpg|thumb|A [[Syrphid fly]] on a [[Grape hyacinth]]]]
:::* [[Diptera]] (true flies)
:::* [[Protodiptera]] †
::: [[Amphiesmenoptera]]''
:::* [[Trichoptera]] (caddisflies)
:::* [[Lepidoptera]] (butterflies, moths, skippers)
Insects can be divided into two groups, historically treated as subclasses: Apterygota (wingless) and Pterygota (winged). The Apterygota consists of two primitively wingless orders - Archaeognatha (bristletails) and Thysanura (silverfish). Archaeognatha makes up the Monocondylia (based on mandibular morphology) while Thysanura and Pterygota are grouped together as Dicondylia. It is possible that the Thysanura itself is not [[monophyletic]], with the family [[Lepidotrichidae]] a [[sister group]] to the Dicondylia (Pterygota + the remaining Thysanura).
Paleoptera and Neoptera are the winged orders of insects, separated by the presence of sclerites and musculature that allow for folding of the wings flat over the abdomen in the latter group. Neoptera can further be divided into hemimetabolous ([[Polyneoptera]] & [[Paraneoptera]]) and Holometabolous groups. It has proven particularly difficult to elucidate interordinal relationships within Polyneoptera. Phasmatodea and Embiidina have been suggested to form Eukinolabia.<ref>Terry, M. D. and M. F. Whiting. 2005. Mantophasmatodea and phylogeny of the lower neopterous insects. Cladistics 21(3): 240-257</ref> Mantodea, Blattodea & Isoptera are thought to form a monophyletic group termed [[Dictyoptera]].<ref>Lo, N., G. Tokuda, H. Watanabe, H. Rose, M. Slaytor, K. Maekawa, C. Bandi, and H. Noda. 2000. Evidence from multiple gene sequences indicates that termites evolved from wood-feeding cockroaches. Current Biology 10(13):801-804.</ref> Paraneoptera has turned out to be more closely related to Endopterygota than to the rest of the Exopterygota. The recent molecular finding that the traditional louse orders [[Mallophaga]] and [[Anoplura]] are derived from within [[Psocoptera]] has led to the new taxon [[Psocodea]].<ref>Johnson, K. P., Yoshizawa, K. and V. S. Smith. 2004. Multiple origins of parasitism in lice. Proceedings of the Royal Society of London 271: 1771-1776.</ref>
It is quite likely that Exopterygota is [[paraphyletic]] in regards to Endopterygota. Contentious matters include Strepsiptera and Diptera grouped together as Halteria based on a reduction of one of the wing pairs - a position not well-supported in the entomological community.<ref>Bonneton, F., F. G. Brunet, J. Kathirithamby, V. Laudet. 2006. The rapid divergence of the ecdysone receptor is a synapomorphy for Mecopterida that clarifies the Strepsiptera problem. Insect Molecular Biology 15(3):351-362.</ref> The Neuropterida are often "lumped" or "split" on the whims of the taxonomist. Fleas are now thought to be closely related to boreid mecopterans.<ref>Whiting, M.F. 2002. Mecoptera is paraphyletic: multiple genes and phylogeny of Mecoptera and Siphonaptera. Zoologica Scripta 31(1): 93-104.</ref> Many questions remain to be answered when it comes to basal relationships amongst endopterygote orders, particularly Hymenoptera.
==Relationship to humans==
[[Image:Aedes aegypti biting human.jpg|thumb|right|''[[Aedes aegypti]]'', a parasite, and vector of [[dengue fever]] and [[yellow fever]]]]
Many insects are considered pests by humans. Insects commonly regarded as pests include those that are parasitic ([[mosquito]]es, [[lice]], [[bed bug]]s), transmit diseases ([[mosquito]]es, [[fly|flies]]), damage structures ([[termite]]s), or destroy agricultural goods ([[locust]]s, [[weevil]]s). Many [[entomologist]]s are involved in various forms of [[pest (animal)|pest]] control, often using [[insecticides]], but more and more relying on methods of [[Biological pest control|biocontrol]].
Although pest insects attract the most attention, many insects are beneficial to the [[environment (biophysical)|environment]] and to [[human]]s. Some [[pollination|pollinate]] [[flowering plant]]s (for example [[wasp]]s, [[bee]]s, [[butterfly|butterflies]], [[ant]]s). Pollination is a trade between plants that need to reproduce, and pollinators that receive rewards of [[nectar (plant)|nectar]] and [[pollen]]. A serious environmental problem today is the [[pollinator decline|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.
Insects also produce useful substances such as [[honey]], [[wax]], [[lacquer]] and [[silk]]. [[Honey bee]]s have been cultured by humans for thousands of years for honey, although contracting for crop pollination is becoming more significant for [[beekeeper]]s. The [[silkworm]] has greatly affected human history, as [[Silk Road|silk-driven trade]] established relationships between China and the rest of the world. [[Fly]] larvae ([[maggot]]s) were formerly used to [[Maggot therapy|treat wounds]] to prevent or stop [[gangrene]], as they would only consume dead flesh. This treatment is finding modern usage in some hospitals. Adult insects such as crickets, and insect larvae of various kinds are also commonly used as fishing bait.
[[Image:Chorthippus biguttulus f 8835.jpg|thumb|left|''Chorthippus biguttulus'', a grasshopper]]
In some parts of the world, insects are used for human food ("[[Entomophagy]]"), while being a [[taboo]] in other places. There are proponents of developing this use to provide a major source of [[protein]] in human [[nutrition]]. Since it is impossible to entirely eliminate pest insects from the human food chain, insects already are present in many foods, especially grains. Most people do not realize that [[food safety]] laws in many countries do not prohibit insect parts in food, but rather limit the quantity. According to [[cultural materialism|cultural materialist]] anthropologist [[Marvin Harris]], the eating of insects is taboo in cultures that have protein sources that require less work, like farm birds or cattle.
Many insects, especially [[beetle]]s, are [[scavenger]]s, feeding on dead animals and fallen trees, [[recycling]] the biological materials into forms found useful by other [[organism]]s, and insects are responsible for much of the process by which [[topsoil]] is created. The [[ancient Egyptian religion]] adored [[dung beetles]] and represented them as beetle-shaped [[amulet]]s, or scarabs.
The most useful of all insects are [[insectivore]]s, those that feed on other insects. Many insects can potentially reproduce so quickly that if all of their offspring were to survive, they could literally bury the earth in a single season. However, for any given insect one can name, whether it is considered a pest or not, there will be one to hundreds of species of insects that are either [[parasitoid]]s or [[predator]]s upon it, and play a significant role in controlling it. This role in ecology is usually assumed to be primarily one of [[bird]]s, but insects, though less glamorous, are much more significant.
Human attempts to control pests by insecticides can backfire, because important but unrecognised insects already helping to control pest populations are also killed by the poison, leading eventually to population explosions of the pest species.
==Quotations==
*"''Something in the insect seems to be alien to the habits, morals, and psychology of this world, as if it had come from some other planet: more monstrous, more energetic, more insensate, more atrocious, more infernal than our own.''"
::—[[Maurice Maeterlinck]] (1862–1949)
*When asked what can be learned about the Creator by examining His work, [[J.B.S. Haldane]] said "''an inordinate fondness for beetles''."
*"''To understand the success of insects is to appreciate our own shortcomings''" —[[Thomas Eisner]]
==See also==
{{Wikispecies|Insecta}}
{{Commons|Insect}}
*[[Animal]]
*[[Flying and gliding animals]]
*[[Entomology]]
*[[Invertebrate]]
*[[Prehistoric insect]]
*[[Insect flight]]
*[[Insect ecology]]
*[[:Category:Insect-borne diseases]]
==References==
{{reflist|2}}
==Further reading==
*Davidson, E. (ed.) 1981. Pathogenesis of Invertebrate Micorobial Diseases. Allanheld, Osmun & Co. Publishers, Inc., Totowa, New Jersey, USA. 562 pages.
*Davidson, E. 2006. ''Big Fleas Have Little Fleas: How Discoveries of Invertebrate Diseases Are Advancing Modern Science'' University of Arizona Press, Tucson, 208 pages, ISBN 0-8165-2544-7
*Davidson, RH and William F. Lyon. 1979 ''Insect Pests of Farm, Garden, and Orchard.'' John Wiley & Sons., New York. 596 pages, ISBN 0-471-86314-9.
*{{cite book|author=[[David Grimaldi|Grimaldi, D.]] and [[Michael S. Engel|Engel, M.S.]] |title=Evolution of the Insects|year=2005|publisher=[[Cambridge University Press]]|id=ISBN 0-521-82149-5}}
*Reimer, N.J., J.W. Beardsley, and G. C. Jahn 1990. Pest ants in the Hawaiian Islands. In R. Vander Meer, K. Jaffe, and A. Cedena [eds.], "Applied Myrmecology: a world perspective." Westview Press, Oxford, 40-50.
*Triplehorn, Charles A. and Norman F. Johnson (2005-05-19). Borror and DeLong's Introduction to the Study of Insects, 7th edition, Thomas Brooks/Cole. ISBN 0-03-096835-6. — a classic textbook in North America
*{{cite book|author=[[David Grimaldi|Grimaldi, D.]] and [[Michael S. Engel|Engel, M.S.]] |title=Evolution of the Insects|year=2005|publisher=[[Cambridge University Press]]|id=ISBN 0-521-82149-5}} — an up to date review of the evolutionary history of the insects
*{{cite book|author=[[Alex Rasnitsyn|Rasnitsyn, A.P.]] and Quicke, D.L.J.|title=History of Insects|year=2002|publisher=[[Kluwer Academic Publishers]]|id=ISBN 1-4020-0026-X}} — detail coverage of various aspects of the evolutionary history of the insects
*{{cite book|author= Biewener, Andrew A.|title=Animal Locomotion|year=2003|publisher=Oxford University Press|id=ISBN 0-19-850022-X}}
*{{cite book|author=Merritt, RW, KW Cummins, and MB Berg|title=An Introduction To The Aquatic Insects Of North America|year=2007|publisher=Kendall Hunt Publishing Company|id=ISBN 0-7575-4128-3}}
==External links==
* [http://tolweb.org/Insecta/8205 Tree of Life Project] – Insecta, [http://tolweb.org/movies/Insecta/8205 Insecta Movies]
* [http://www.entomology.umn.edu/cues/4015/morpology/ Insect Morphology] Overview of insect external and internal anatomy
* [http://www.urbanext.uiuc.edu/insects Let's Talk About Insects] For students ages 9-11 years, learn how insects grow and develop (metamorphosis), and learn the importance of insects in our environment. (Also in [http://www.urbanext.uiuc.edu/insects_sp Spanish])
* [http://www.ub.es/dpep/meganeura/meganeura.htm Meganeura] Insect evolution and fossil record.
* [http://fossilinsects.net/index.htm IPS] International Palaeoentological Society.
* [http://ufbir.ifas.ufl.edu/ UF Book of Insect Records] Insect records
* [http://www.life.uiuc.edu/delcomyn/RSInsectWalking.html/ Insect Walking] Research into Insect Locomotion at the University of Illinois
* [http://www.berkeley.edu/news/media/releases/2002/09/rfull/locomotion.html/ Press Release 2002 on research into polypodal locomotion]
* [http://www.insectclopedia.com/ Insectclopedia] Insect research portal
* [http://www.food-insects.com/ Insects as Food] Insects as a food resource.
* [http://www.ndsu.edu/entomology/topics/culture.htm Insects and human culture]
* [http://www.insectstore.com Information on keeping, breeding and rearing] Insects and invertebrates.
* [http://www.ars.usda.gov/pandp/docs.htm?docid=10919 Bug Bytes] Reference library of digitized insect sounds.
* [http://www.insects.org/index.html INSECTS .org] Insect appreciation.
* [http://www.nzzfolio.ch/www/d80bd71b-b264-4db4-afd0-277884b93470/showarticle/d217322c-e20e-4870-84c4-ec8839e4ee02.aspx The Unexpected Apocalypse]. Entomologist May Berenbaum about a world without insects.
* [http://news.bbc.co.uk/1/hi/world/americas/4808342.stm Pentagon plans cyber-insect army]
* [http://www.antiquebooks.net/readpage.html#insects Introduction to the Natural History and Classification of Insects in a Series of Familiar Letters with Engravings, Priscilla Wakefield, 1816] A free to read book
* [http://www.earthlife.net/insects/anatomy.html Earthlife Web] - Insect Morphology and Anatomy
* [http://creatures.ifas.ufl.edu/ Featured Creatures] Hundreds of species and groups
* [http://woodypest.ifas.ufl.edu/ WoodyBug] S.E. U.S. woody ornamental pests and beneficials
* [http://vector.ifas.ufl.edu/ Public Health Pest Control] - EPA national manual on public health arthropods
* [http://ca.youtube.com/watch?v=sSk_ev1eZec Video: Life Cycle of a Honeybee]
===Image resources===
* [http://bugguide.net/ BugGuide] Photographs, life history and identification of North American arthropods, especially insects
* [http://www.livescience.com/insects/ LiveScience: Insects] Insect information and user-submitted insect pictures
* [http://www.me.esalq.usp.br/index_i.php ESALQ Entomological Museum] 6000 insect pictures. Brazilian collection (ESALQ/USP).
* [http://www.cirrusimage.com/ North American Insects] 4,000 large format insect pictures. Creative Commons licensed
* [http://www.floridanaturepictures.com/insects/insects.html Pictures of Florida insects]
* [http://www.insectimages.org/ InsectImages.org] 24,000 high resolution insect photographs. Free for non-profit educational uses.
{{Arthropods}}
[[Category:Arthropods]]
[[Category:Entomology]]
[[Category:Insects| ]]
{{Link FA|ar}}
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{{Link FA|vi}}
[[ang:Ceorfdēor]]
[[ar:حشرة]]
[[an:Insecta]]
[[ast:Inseutu]]
[[zh-min-nan:Khun-thiông]]
[[be:Насякомыя]]
[[bs:Insekti]]
[[br:Amprevan]]
[[bg:Насекоми]]
[[ca:Insecte]]
[[cs:Hmyz]]
[[cy:Pryf]]
[[da:Insekt]]
[[de:Insekten]]
[[et:Putukad]]
[[el:Έντομα]]
[[es:Insecta]]
[[eo:Insekto]]
[[eu:Intsektu]]
[[fa:حشرات]]
[[fo:Skordýr]]
[[fr:Insecte]]
[[fy:Ynsekten]]
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[[hr:Kukci]]
[[io:Insekto]]
[[id:Serangga]]
[[ia:Insecto]]
[[is:Skordýr]]
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[[he:חרקים]]
[[ht:Ensèk]]
[[la:Insecta]]
[[lv:Kukaiņi]]
[[lb:Insekten]]
[[lt:Vabzdžiai]]
[[li:Insekte]]
[[ln:Nyama ekɛ́]]
[[hu:Rovarok]]
[[mk:Инсект]]
[[ml:ഷഡ്പദം]]
[[ms:Serangga]]
[[nl:Insecten]]
[[nds-nl:Insekt]]
[[ja:昆虫類]]
[[no:Insekter]]
[[nn:Insekt]]
[[oc:Insecta]]
[[pl:Owady]]
[[pt:Inseto]]
[[ro:Insectă]]
[[qu:Palama]]
[[ru:Насекомые]]
[[sc:Babbalottu]]
[[stq:Insekte]]
[[simple:Insect]]
[[sk:Hmyz]]
[[sl:Žuželke]]
[[sr:Инсекти]]
[[sh:Insekt]]
[[su:Serangga]]
[[fi:Hyönteiset]]
[[sv:Insekter]]
[[tl:Kulisap]]
[[ta:பூச்சி]]
[[te:కీటకము]]
[[th:แมลง]]
[[vi:Côn trùng]]
[[tg:Ҳашарот]]
[[to:ʻinisēkite]]
[[tr:Böcek]]
[[uk:Комахи]]
[[wa:Inseke]]
[[yi:אינסעקט]]
[[zh-yue:昆蟲]]
[[bat-smg:Vabzdē]]
[[zh:昆虫]]