Evolution has produced enormous variety in insects. Pictured are some possible shapes of antennae.
A pie chart of described eukaryote species, showing just over half of these to be insects
Insects with population trends documented by the International Union for Conservation of Nature, for orders Collembola, Hymenoptera, Lepidoptera, Odonata, and Orthoptera. Of 203 insect species that had such documented population trends in 2013, 33% were in decline.
Stylized diagram of insect digestive tract showing malpighian tubule, from an insect of the order Orthoptera
Bumblebee defecating. Note the contraction of the abdomen to provide internal pressure
The tube-like heart (green) of the mosquito Anopheles gambiae extends horizontally across the body, interlinked with the diamond-shaped wing muscles (also green) and surrounded by pericardial cells (red). Blue depicts cell nuclei.
The different forms of the male (top) and female (bottom) tussock moth Orgyia recens is an example of sexual dimorphism in insects.
Gulf fritillary life cycle, an example of holometabolism.
Most insects have compound eyes and two antennae.
A cathedral mound created by termites (Isoptera).
White-lined sphinx moth feeding in flight
The backswimmer Notonecta glauca underwater, showing its paddle-like hindleg adaptation
Perhaps one of the most well-known examples of mimicry, the viceroy butterfly (top) appears very similar to the monarch butterfly (bottom).
European honey bee carrying pollen in a pollen basket back to the hive
Aedes aegypti, a parasite, is the vector of dengue fever and yellow fever
Because they help flowering plants to cross-pollinate, some insects are critical to agriculture. This European honey bee is gathering nectar while pollen collects on its body.
A robberfly with its prey, a hoverfly. Insectivorous relationships such as these help control insect populations.
The common fruit fly Drosophila melanogaster is one of the most widely used organisms in biological research.

Insects (from Latin insectum) are pancrustacean hexapod invertebrates of the class Insecta.

- Insect
Evolution has produced enormous variety in insects. Pictured are some possible shapes of antennae.

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An Anthomyiidae species showing characteristic dipteran features: large eyes, small antennae, sucking mouthparts, single pair of flying wings, hindwings reduced to clublike halteres
Fossil brachyceran in Baltic amber. Lower Eocene, c. 50 million years ago
Fossil nematoceran in Dominican amber. Sandfly, Lutzomyia adiketis (Psychodidae), Early Miocene, c. 20 million years ago
Gauromydas heros is the largest fly in the world.
Head of a horse-fly showing large compound eyes and stout piercing mouthparts
A head of a fly, showing the two compound eyes and three simple eyes clearly.
A cranefly, showing the hind wings reduced to drumstick-shaped halteres
Tabanid fly in flight
Mating anthomyiid flies
Life cycle of stable fly Stomoxys calcitrans, showing eggs, 3 larval instars, pupa, and adult
A calliphorid "bubbling"
The large bee-fly, Bombylius major, is a Batesian mimic of bees.
Petrus Christus's 1446 painting Portrait of a Carthusian has a musca depicta (painted fly) on a trompe-l'œil frame.
An Anopheles stephensi mosquito drinking human blood. The species carries malaria.
Diptera in research: Drosophila melanogaster fruit fly larvae being bred in tubes in a genetics laboratory
Casu marzu is a traditional Sardinian sheep milk cheese that contains larvae of the cheese fly, Piophila casei.

Flies are insects of the order Diptera, the name being derived from the Greek δι- di- "two", and πτερόν pteron "wing".


Bombus muscorum drinking nectar with its long proboscis
Symphyta, without a waist: the sawfly Arge pagana
Apocrita, with narrow waist: the wasp Vespula germanica

Hymenoptera is a large order of insects, comprising the sawflies, wasps, bees, and ants.


The external appearance of the giant northern termite Mastotermes darwiniensis is suggestive of the close relationship between termites and cockroaches.
Macro image of a worker.
Close-up view of a worker's head
Diagram showing a wing, along with the clypeus and leg
Caste system of termites
A – King
B – Queen
C – Secondary queen
D – Tertiary queen
E – Soldiers
F – Worker
A young termite nymph. Nymphs first moult into workers, but others may further moult to become soldiers or alates.
Termite, and shed wings from other termites, on an interior window sill. Shedding of wings is associated with reproductive swarming.
Alates swarming during nuptial flight after rain
Termite faecal pellets
Crab spider with a captured alate
A Matabele ant (Megaponera analis) kills a Macrotermes bellicosus termite soldier during a raid.
Hordes of Nasutitermes on a march for food, following and leaving trail pheromones
Termites rush to a damaged area of the nest.
Nasute termite soldiers on rotten wood
Rhizanthella gardneri is the only orchid known to be pollinated by termites.
An ant raiding party collecting Pseudocanthotermes militaris termites after a successful raid
An arboreal termite nest in Mexico
Termite nest in a Banksia, Palm Beach, Sydney.
Nasutiterminae shelter tubes on a tree trunk provide cover for the trail from nest to forest floor.
Termite mound as an obstacle on a runway at Khorixas (Namibia)
Termite damage on external structure
Termite damage in wooden house stumps
Mozambican boys from the Yawo tribe collecting flying termites
These flying alates were collected as they came out of their nests in the ground during the early days of the rainy season.
Scientists have developed a more affordable method of tracing the movement of termites using traceable proteins.
The pink-hued Eastgate Centre
alt=. These termite mounds have a base shaped like the base of a tree, about two meters wide and a meter high. From this base, rounded chimneys from half a meter to a meter in diameter rise to a total height of about four or five meters. The chimneys are fused together with ridges between, and terminate in rounded pinnacles at the top.|Cathedral mounds in the Northern Territory, Australia
alt=. Hundreds of compass termite mounds are visible in this photo of a field in northern Australia. The chisel-shaped mounds range from several centimeters to several meters in height.|Mounds of "compass" or "magnetic" termites (Amitermes) oriented north–south, thereby avoiding mid-day heat
alt=. This termite mound is about three meters in height and four meters across. The mound chimneys are about a meter in diameter and fuse together to form a rounded top.|Termite mound in Queensland, Australia
alt=. The photographer has broken off a piece of a mound to show the mound's interior. Dozens of tunnels have been exposed, and hundreds of soldiers have emerged to guard the breech in the wall.|Termites in a mound, Analamazoatra Reserve, Madagascar
Termite mound in Namibia

Termites are eusocial insects that are classified at the taxonomic rank of infraorder Isoptera, or alternatively as epifamily Termitoidae, within the order Blattodea (along with cockroaches).

Lifestages of a holometabolous insect (wasp). Egg is not shown. Third, fourth, and fifth images depict different ages of pupae.


Form of insect development which includes four life stages: egg, larva, pupa, and imago .

Form of insect development which includes four life stages: egg, larva, pupa, and imago .

Lifestages of a holometabolous insect (wasp). Egg is not shown. Third, fourth, and fifth images depict different ages of pupae.
Various insect eggs.
Scarabaeiform larva and exarate pupae of a rhinoceros beetle.
Rhopalomyia solidaginis, pupa and emerging adult.

The first stage of the insect life cycle is the egg, or embryo, for all developmental strategies.

Diagram of biramous leg of a trilobite; Agnostus spp.

Arthropod leg

Form of jointed appendage of arthropods, usually used for walking.

Form of jointed appendage of arthropods, usually used for walking.

Diagram of biramous leg of a trilobite; Agnostus spp.
Crustacean appendages
Micrograph of housefly leg
Diagram of a spider leg and pedipalp – the pedipalp has one fewer segment
The leg of a squat lobster, showing the segments; the ischium and merus are fused in many decapods
Seven-segmented legs of Scutigera coleoptrata
Zabalius aridus showing full leg anatomy, including plantulae under each tarsomere
Diagram of a typical insect leg
Acanthacris ruficornis, legs saltatorial, femora with bipennate muscle attachments, spines on tibiae painfully effective in a defensive kick
Robber fly (Asilidae), showing tarsomeres and pretarsi with ungues, pulvilli and empodia
Webspinner, Embia major, front leg showing enlarged tarsomere, which contains the silk-spinning organs
Bruchine with powerful femora used for escape from hard-shelled seed
Expression of Hox genes in the body segments of different groups of arthropod, as traced by evolutionary developmental biology. The Hox genes 7, 8, and 9 correspond in these groups but are shifted (by heterochrony) by up to three segments. Segments with maxillopeds have Hox gene 7. Fossil trilobites probably had three body regions, each with a unique combination of Hox genes.

The legs of insects and myriapods are uniramous.

Bumblebee's wing.

Insect wing

Bumblebee's wing.
Venation of insect wings, based on the Comstock–Needham system
The diamond-shaped alary muscles (green) of the mosquito Anopheles gambiae and their structural relationship to the tube-like heart (also in green). Red depicts pericardial cells, blue cell nuclei.
Australian emperor in flight; it uses the direct flight mechanism.
Holotype wing of the extinct Cimbrophlebia brooksi. 49.5 Million Years old; "Boot Hill", Klondike Mountain Formation, Washington, USA.
Transition of scales color on a butterfly wing (30x magnification).

Insect wings are adult outgrowths of the insect exoskeleton that enable insects to fly.

Two Schistocerca gregaria nymphs beside an adult

Nymph (biology)

Two Schistocerca gregaria nymphs beside an adult

In biology, a nymph is the immature form of some invertebrates, particularly insects, which undergoes gradual metamorphosis (hemimetabolism) before reaching its adult stage.


Wasps are paraphyletic, consisting of the clade Apocrita without ants and bees, which are not usually considered to be wasps. The Hymenoptera also contain the somewhat wasplike Symphyta, the sawflies. The familiar common wasps and yellowjackets belong to one family, the Vespidae.
Male Electrostephanus petiolatus fossil from the Middle Eocene, preserved in Baltic amber
Social wasps constructing a paper nest
Potter wasp building mud nest, France. The latest ring of mud is still wet.
European hornet, Vespa crabro
Sand wasp Bembix oculata (Crabronidae) feeding on a fly after paralysing it with its sting
Spider wasp (Pompilidae) dragging a jumping spider (Salticidae) to provision a nest
Wasp waist, c. 1900, demonstrated by Polaire, a French actress famous for this silhouette
Detail of Botticelli's Venus and Mars, 1485, with a wasp's nest on right, probably a symbol of the Vespucci family (Italian vespa, wasp) who commissioned the painting.
, one of nine Royal Navy warships to bear the name
Megascolia procer, a giant solitary species from Java in the Scoliidae. This specimen's length is 77mm and its wingspan is 115mm.{{efn | Specimen measured from photograph.}}<ref name=Sarrazin>{{cite journal | last1=Sarrazin | first1=Michael | last2=Vigneron | first2=Jean Pol | last3=Welch | first3=Victoria | last4=Rassart | first4=Marie | title=Nanomorphology of the blue iridescent wings of a giant tropical wasp Megascolia procer javanensis (Hymenoptera) | journal=Phys. Rev. | date=5 November 2008 | volume=E 78 | issue=5 | pages=051902 | doi=10.1103/PhysRevE.78.051902 | pmid=19113150 | arxiv=0710.2692 | bibcode=2008PhRvE..78e1902S | s2cid=30936410 }} Measurement scale on Figure 1.</ref>
Megarhyssa macrurus, a parasitoid. The body of a female is 50mm long, with a c. 100mm ovipositor
Tarantula hawk wasp dragging an orange-kneed tarantula to her burrow; it has the most painful sting of any wasp.
Minute pollinating fig wasps, Pleistodontes: the trees and wasps have coevolved and are mutualistic.
Latina rugosa planidia (arrows, magnified) attached to an ant larva; the Eucharitidae are among the few parasitoids able to overcome the strong defences of ants.
The Chrysididae, such as this Hedychrum rutilans, are known as cuckoo or jewel wasps for their parasitic behaviour and metallic iridescence.
European beewolf Philanthus triangulum provisioning her nest with a honeybee
Wasp beetle Clytus arietis is a Batesian mimic of wasps.
Bee-eaters such as Merops apiaster specialise in feeding on bees and wasps.
Encarsia formosa, a parasitoid, is sold commercially for biological control of whitefly, an insect pest of tomato and other horticultural crops.
Tomato leaf covered with nymphs of whitefly parasitised by Encarsia formosa

A wasp is any insect of the narrow-waisted suborder Apocrita of the order Hymenoptera which is neither a bee nor an ant; this excludes the broad-waisted sawflies (Symphyta), which look somewhat like wasps, but are in a separate suborder.


Spiders (order Araneae) are air-breathing arthropods that have eight legs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude silk.

Spiders (order Araneae) are air-breathing arthropods that have eight legs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude silk.

A syrphid fly captured in the web of a spider
Cheiracanthium punctorium, displaying fangs
This jumping spider's main ocelli (center pair) are very acute. The outer pair are "secondary eyes" and there are other pairs of secondary eyes on the sides and top of its head.
Eyes of the jumping spider, Plexippus paykulli
Image of a spider leg: 1–coxa; 2–trochanter; 3–femur; 4–patella; 5–tibia; 6–metatarsus; 7–tarsus; 8–claws
An orb weaver producing silk from its spinnerets
Goliath birdeater (Theraphosa blondi), the largest spider
A jumping spider seen in Chennai.
Crab spider with prey
The Phonognatha graeffei or leaf-curling spider's web serves both as a trap and as a way of making its home in a leaf.
A trapdoor spider in the genus Cyclocosmia, an ambush predator
Portia uses both webs and cunning, versatile tactics to overcome prey.
An ant-mimicking jumping spider
Threat display by a Sydney funnel-web spider (Atrax robustus).
The large orb web of Araneus diadematus (European garden spider).
Nephila clavata, a golden orb weaver
A funnel web.
Spider preserved in amber
Ryuthela sasakii, a member of the Liphistiidae
A Mexican red-kneed tarantula Brachypelma hamorii
Leucauge venusta, an orb-web spider
Cooked tarantulas are considered a delicacy in Cambodia.
This Moche ceramic depicts a spider, and dates from around 300 CE.
The tiny male of the golden orb weaver (Trichonephila clavipes) (near the top of the leaf) is protected from the female by producing the right vibrations in the web, and may be too small to be worth eating.
Orange spider egg sac hanging from ceiling
Gasteracantha mammosa spiderlings next to their eggs capsule
Wolf spider carrying its young on its abdomen

Unlike insects, spiders do not have antennae.

Diagram briefly covering pollination


Transfer of pollen from an anther of a plant to the stigma (female part) of a plant, later enabling fertilisation and the production of seeds, most often by an animal or by wind.

Transfer of pollen from an anther of a plant to the stigma (female part) of a plant, later enabling fertilisation and the production of seeds, most often by an animal or by wind.

Diagram briefly covering pollination
Female Xylocopa with pollen collected from night-blooming cereus
Bee pollinating a plum tree (Prunus cerasifera)
Melissodes desponsus covered in pollen
Hummingbirds typically feed on red flowers
A European honey bee collects nectar, while pollen collects on its body.
Africanized honey bees immersed in Opuntia engelmannii cactus Pollen
Diadasia bee straddles cactus carpels
The wasp Mischocyttarus rotundicollis transporting pollen grains of Schinus terebinthifolius
An Andrena bee gathers pollen from the stamens of a rose. The female carpel structure appears rough and globular to the left.
Bombus ignitus, a popular commercial pollinator in Japan and China
The graph shows the number of honeybee colonies in the U.S. from 1982 to 2015,
The graph shows the average dollar amount per colonies received by beekeepers depending on the pollinated crop.
Geranium incanum, like most geraniums and pelargoniums, sheds its anthers, sometimes its stamens as well, as a barrier to self-pollination. This young flower is about to open its anthers, but has not yet fully developed its pistil.
The lower two of these Geranium incanum flowers have opened their anthers, but not yet their stigmas. Note the change of colour that signals to pollinators that they are ready for visits. The uppermost flower is somewhat more mature than the others and has already shed its stamens.
This Geranium incanum flower has shed its stamens, and deployed the tips of its pistil without accepting pollen from its own anthers. (It might of course still receive pollen from younger flowers on the same plant.)

The majority of these pollinators are insects, but about 1,500 species of birds and mammals visit flowers and may transfer pollen between them.