Insect

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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A tau emerald (Hemicordulia tau) dragonfly has flight muscles attached directly to its wings.

Insect flight

A tau emerald (Hemicordulia tau) dragonfly has flight muscles attached directly to its wings.
Hoverfly (Xanthogramma pedissequum) has indirect flight musculature.
Frenulo-retinacular wing coupling in male and female moths
Reconstruction of a Carboniferous insect, the Palaeodictyopteran Mazothairos
Mayfly nymph with paired abdominal gills
Leg of a trilobite, an early arthropod. The internal branch made of endites is at the top; the smaller external branch made of exites is below. Trueman proposed that an endite and an exite fused to form a wing.
Direct flight: muscles attached to wings. Large insects only
The Odonata (dragonflies and damselflies) have direct flight musculature, as do mayflies.
Indirect flight: muscles make thorax oscillate in most insects
The Neoptera, including butterflies and most other insects, have indirect flight musculature
Clap 1: wings close over back
Clap 2: leading edges touch, wing rotates around leading edge, vortices form
Clap 3: trailing edges close, vortices shed, wings close giving thrust
Fling 1: wings rotate around trailing edge to fling apart
Fling 2: leading edge moves away, air rushes in, increasing lift
Fling 3: new vortex forms at leading edge, trailing edge vortices cancel each other, perhaps helping flow to grow faster (Weis-Fogh 1973)

Insects are the only group of invertebrates that have evolved wings and flight.

Mecoptera

Male Panorpa dubia. A, Body in lateral view; B–D. male genital bulb and gonostyli. B, dorsal view; C, ventral view; D, lateral view. ep, epandrium; gcx, gonocoxite; gs, gonostylus; hv, hypovalva; hyp, hypandrium. Scale bars represent 3 mm in A, 1 mm in B–D
A Panorpid scorpionfly feeding on a dead insect
Panorpa communis mating
Hangingflies have distinct mating behaviour.
The raised scorpion-like tail of the male has earned the scorpionflies a sinister reputation, but they do not sting.
Juracimbrophlebia ginkgofolia (Cimbrophlebiidae) reconstruction, Jurassic; China
Jurassipanorpa sticta (Panorpidae), Jurassic; China
Forewing of Dinokanaga andersoni (Dinopanorpidae), Eocene; Washington state

Mecoptera (from the Greek: mecos = "long", ptera = "wings") is an order of insects in the superorder Endopterygota with about six hundred species in nine families worldwide.

Cladogram (family tree) of a biological group. The last common ancestor is the vertical line stem at the bottom. The blue and red subgroups are clades; each shows its common ancestor stem at the bottom of the subgroup branch. The green subgroup is not a clade; it is a paraphyletic group, because it excludes the blue branch which has descended from the same common ancestor. The green and blue subgroups together form a clade again.

Clade

Group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree.

Group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree.

Cladogram (family tree) of a biological group. The last common ancestor is the vertical line stem at the bottom. The blue and red subgroups are clades; each shows its common ancestor stem at the bottom of the subgroup branch. The green subgroup is not a clade; it is a paraphyletic group, because it excludes the blue branch which has descended from the same common ancestor. The green and blue subgroups together form a clade again.
Early phylogenetic tree by Haeckel, 1866. Groups once thought to be more advanced, such as birds ("Aves"), are placed at the top.
Gavialidae, Crocodylidae and Alligatoridae are clade names that are here applied to a phylogenetic tree of crocodylians.
Cladogram of modern primate groups; all tarsiers are haplorhines, but not all haplorhines are tarsiers; all apes are catarrhines, but not all catarrhines are apes; etc.

Many commonly named groups – rodents and insects, for example – are clades because, in each case, the group consists of a common ancestor with all its descendant branches.

Diagram briefly covering pollination

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.

Spider

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.

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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.

Hymenoptera

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.

Eggs of various birds, a reptile, various cartilaginous fish, a cuttlefish and various butterflies and moths. (Click on image for key)

Egg

Organic vessel containing the zygote in which an embryo develops until it can survive on its own, at which point the animal hatches.

Organic vessel containing the zygote in which an embryo develops until it can survive on its own, at which point the animal hatches.

Eggs of various birds, a reptile, various cartilaginous fish, a cuttlefish and various butterflies and moths. (Click on image for key)
Diagram of a chicken egg in its 9th day. Membranes: allantois, chorion, amnion, and vitellus/ yolk.
Six commercial eggs — view from the top against a white background
Salmon fry hatching. The larva has grown around the remains of the yolk and the remains of the soft, transparent egg are discarded.
Guillemot eggs
Turtle eggs in a nest dug by a female common snapping turtle (Chelydra serpentina)
Orange-peel doris (Acanthodoris lutea), a nudibranch, in tide pool laying eggs
Microlecithal eggs from the roundworm Toxocara
Microlecithal eggs from the flatworm Paragonimus westermani
Frogspawn is mesolecithal.
A baby tortoise begins to emerge "fully developed" from its macrolecithal egg.
Chocolate Easter eggs hidden as part of an egg hunt
An average whooping crane egg is {{convert|102|mm|abbr=on}} long and weighs {{convert|208|g|oz|abbr=on}}
Eurasian oystercatcher eggs camouflaged in the nest
Egg of a senegal parrot, a bird that nests in tree holes, on a {{convert|1|cm|in|abbr=on}} grid
Eggs of ostrich, emu, kiwi and chicken
Finch egg next to American dime
Eggs of duck, goose, guineafowl and chicken
Eggs of ostrich, cassowary, chicken, flamingo, pigeon and blackbird
Egg of an emu
Egg from a chicken compared to a 1 euro coin, great tit egg and a corn grain
Bird nest with brown marbling eggs of a robin
A spherical chicken egg
Insect eggs, in this case those of the Emperor gum moth, are often laid on the underside of leaves.
Fish eggs, such as these herring eggs are often transparent and fertilized after laying.
Skates and some sharks have a uniquely shaped egg case called a mermaid's purse.
A Testudo hermanni emerging fully developed from a reptilian egg.
A Schistosoma mekongi egg.
Eggs of Huffmanela hamo, a nematode parasite in a fish
Eggs of various parasites (mainly nematodes) from wild primates

Eggs are common among invertebrates, including insects, spiders, mollusks, and crustaceans.

Springtail

Isotoma with visible furcula
"Snow flea"
A species of Sminthurinae (Symphypleona: Sminthuridae)
Dicyrtomina sp. on leaf
Anurida maritima on water
Tomocerus sp. from Germany

Springtails (Collembola) form the largest of the three lineages of modern hexapods that are no longer considered insects (the other two are the Protura and Diplura).

Permian–Triassic boundary at Frazer Beach in New South Wales, with the End Permian extinction event located just above the coal layer

Permian–Triassic extinction event

The Permian–Triassic (P–T, P–Tr) extinction event, also known as the End-Permian Extinction and colloquially as the Great Dying, formed the boundary between the Permian and Triassic geologic periods, as well as between the Paleozoic and Mesozoic eras, approximately 251.9 million years ago.

The Permian–Triassic (P–T, P–Tr) extinction event, also known as the End-Permian Extinction and colloquially as the Great Dying, formed the boundary between the Permian and Triassic geologic periods, as well as between the Paleozoic and Mesozoic eras, approximately 251.9 million years ago.

Permian–Triassic boundary at Frazer Beach in New South Wales, with the End Permian extinction event located just above the coal layer
Shell bed with the bivalve Claraia clarai, a common early Triassic disaster taxon.
Sessile filter feeders like this Carboniferous crinoid, the mushroom crinoid (Agaricocrinus americanus), were significantly less abundant after the P–Tr extinction.
Lystrosaurus was by far the most abundant early Triassic land vertebrate.
Map of Pangaea showing where today's continents were at the Permian–Triassic boundary

It was the largest known mass extinction of insects.

Moth

Moths are a paraphyletic group of insects that includes all members of the order Lepidoptera that are not butterflies, with moths making up the vast majority of the order.

Moths are a paraphyletic group of insects that includes all members of the order Lepidoptera that are not butterflies, with moths making up the vast majority of the order.

Basic moth identification features
Poplar hawk-moth caterpillar (Laothoe populi)
Moth from Kerala, India
An adult male pine processionary moth (Thaumetopoea pityocampa). This species is a serious forest pest when in its larval state. Notice the bristle springing from the underside of the hindwing (frenulum) and running forward to be held in a small catch of the forewing, whose function is to link the wings together.
Tobacco hornworm parasitized by braconid wasps
Assorted moths in the University of Texas Insect Collection
Diagram of a plume moth from Robert Hooke's Micrographia
Leaf-shaped moth (Pergesa acteus)
Giant grey moth (Agrius convolvuli)
Oleander hawk-moth or army green moth (Daphnis nerii)
Six-spot burnet moths mating (Zygaena filipendulae)
Protective silk (or similar material) case (cocoon)
Mating pair of Laothoe populi, or poplar hawkmoths, showing two different color variants
White-lined sphinx moth in Colorado, United States
Closeup of a common clothes moth
Giant silk moth (Adelowalkeria tristygma)
Adult emperor moth (Gonimbrasia belina)
A moth on a marble floor in Kolkata, India
Clothes moth, eye
Female rose-myrtle lappet moth hanging on the wooden door

Baculoviruses are parasite double-stranded DNA insect viruses that are used mostly as biological control agents.