Evolution has produced enormous variety in insects. Pictured are some possible shapes of antennae.
Two Schistocerca gregaria nymphs beside an adult
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.

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

- Nymph (biology)

Insects that undergo three-stage metamorphosis lack a pupal stage and adults develop through a series of nymphal stages.

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

10 related topics

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Hemiptera

Fossil planthopper (Fulgoromorpha) from the Early Cretaceous Crato Formation of Brazil, c. 116 mya
Hemipteran mouthparts are distinctive, with mandibles and maxillae modified to form a piercing "stylet" sheathed within a modified labium.
An ant-mimicking predatory bug Myrmecoris gracilis
Aphid giving birth to live female young
Pondskaters are adapted to use surface tension to keep above a freshwater surface.
Adult and nymph Microvelia water bugs using Marangoni propulsion
Leaf galls formed by plant lice (Psyllidae), Chamaesyce celastroides var. stokesii
A twig wilting bug (Coreidae) piercing and sucking sap from a Zinnia
Leafhoppers protected by meat ants
Masked hunter nymph has camouflaged itself with sand grains.
Firebugs, Pyrrhocoris apterus, protect themselves from predators with bright aposematic warning coloration, and by aggregating in a group.
Colony of cottony cushion scale, a pest of citrus fruits
Cochineal scale insects being collected from a prickly pear in Central America. Illustration by José Antonio de Alzate y Ramírez, 1777
Bed bug nymph, Cimex lectularius, engorged with human blood
Deep-fried cicadas, Cryptotympana atrata, in Chinese Shandong cuisine

Hemiptera is an order of insects, commonly called true bugs, comprising over 80,000 species within groups such as the cicadas, aphids, planthoppers, leafhoppers, bed bugs, and shield bugs.

Hemipterans are hemimetabolous, with young nymphs that somewhat resemble adults.

Cockroach

A 40- to 50-million-year-old cockroach in Baltic amber (Eocene)
Domino cockroach Therea petiveriana, normally found in India
Head of Periplaneta americana
A cockroach soon after ecdysis
Cockroaches in research: Periplaneta americana in an electrophysiology experiment
Madagascar hissing cockroaches kept as pets
3 millimeter cockroach nymph
Female Periplaneta fuliginosa with ootheca
Empty ootheca
American cockroach oothecae

Cockroaches (or roaches ) are insects of the order Blattodea, which also includes termites.

The hatchlings are initially bright white nymphs and continue inflating themselves with air, becoming harder and darker within about four hours.

A dragonfly in its final moult, undergoing metamorphosis from its nymph form to an adult

Metamorphosis

Biological process by which an animal physically develops including birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation.

Biological process by which an animal physically develops including birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation.

A dragonfly in its final moult, undergoing metamorphosis from its nymph form to an adult
Incomplete metamorphosis in the grasshopper with different instar nymphs. The largest specimen is adult.
Two types of metamorphosis are shown. In a complete (holometabolous) metamorphosis the insect passes through four distinct phases, which produce an adult that does not resemble the larva. In an incomplete (hemimetabolous) metamorphosis an insect does not go through a full transformation, but instead transitions from a nymph to an adult by molting its exoskeleton as it grows.
Metamorphosis of butterfly (PSF)
Just before metamorphosis, only 24 hours are needed to reach the stage in the next picture.
Almost functional common frog with some remains of the gill sac and a not fully developed jaw
The large external gills of the crested newt
larva
pupa
pupa ready to hatch
adult

Some insects, fish, amphibians, mollusks, crustaceans, cnidarians, echinoderms, and tunicates undergo metamorphosis, which is often accompanied by a change of nutrition source or behavior.

In hemimetabolous insects, immature stages are called nymphs.

Pentatomoidea

Anatomy of the dorsal aspect of a shield bug. A: head; B: thorax; C: abdomen. 1: claws; 2: tarsus; 3: tibia; 4: femur; 8: compound eye; 9: antenna; 10: clypeus; 23: laterotergites (connexivum); 25: pronotum; 26: scutellum; 27: clavus; 28: corium; 29: embolium; 30: hemelytral membrane.

The Pentatomoidea are a superfamily of insects in the Heteroptera suborder of the Hemiptera order.

These prothoracic glands are also present in the nymphs, which are similar to adults except smaller and without wings.

Cicada

A 17-year cicada, Magicicada, Robert Evans Snodgrass, 1930
A chorus cicada, a species endemic to New Zealand
Mesozoic fossil fore wing of Mesogereon superbum, Australia
The giant cicada Prolystra lithographica from Germany Jurassic, about 150–145 million years ago
A Japanese Minminzemi (Hyalessa maculaticollis)
Cicada sound-producing organs and musculature: a, Body of male from below, showing cover-plates; b, From above, showing drumlike tymbals; c, Section, muscles that vibrate tymbals; d, A tymbal at rest; e, Thrown into vibration, as when singing
Eastern cicada killer wasp (Sphecius speciosus) with cicada prey, United States
Cicada disruptively camouflaged on an olive tree
The day-flying cicada Huechys sanguinea warns off predators with its aposematic red and black coloration. (Southeast Asia)
Silver casket with writing utensils, made by the Nuremberg goldsmith Wenzel Jamnitzer (1507/08–1585): a silver cicada is at lower left.
Japanese snuff bottle in the form of a cicada, c. 1900
Jade cicada amulets. Western Han Dynasty 206 BCE – CE 8
Deep-fried Cryptotympana atrata in Shandong cuisine
A teneral cicada that has just emerged and is waiting to dry before flying away
Newly emerged adult cicada held on human fingers
Cicada exuviae after the adult cicada has left
Cicada clinging to the bark of an eastern red cedar tree in Oklahoma

The cicadas are a superfamily, the Cicadoidea, of insects in the order Hemiptera (true bugs).

When the eggs hatch, the newly hatched nymphs drop to the ground and burrow.

Termite

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).

Unlike ants, which undergo a complete metamorphosis, each individual termite goes through an incomplete metamorphosis that proceeds through egg, nymph, and adult stages.

Aphid

Forewing of the early Middle Triassic (early Anisian) aphid Vosegus triassicus
An aphid fossilised in Baltic amber (Eocene)
Front view of wheat aphid, Schizaphis graminum, showing the piercing-sucking mouthparts
Soybean aphid alternates between hosts and between asexual and sexual reproduction.
Aphid giving birth to live young: populations are often entirely female.
The life stages of the green apple aphid (Aphis pomi). Drawing by Robert Evans Snodgrass, 1930
An ant guards its aphids
Ants tending aphids
Ant extracting honeydew from an aphid
Aphid secreting defensive fluid from the cornicles
Aphids on plant host
Aphid with honeydew, from the anus, not the cornicles
Parasitoid braconid wasp ovipositing in black bean aphid
Green peach aphid, Myzus persicae, killed by the fungus Pandora neoaphidis (Entomophthorales)

Aphids are small sap-sucking insects and members of the superfamily Aphidoidea.

A typical life cycle involves flightless females giving live birth to female nymphs—who may also be already pregnant, an adaptation scientists call telescoping generations—without the involvement of males.

Odonata

The giant Upper Carboniferous dragonfly ancestor, Meganeura monyi, had a wingspan of about 680 mm. Museum of Toulouse
Gomphus vulgatissimus with prey
With prey
Male blue ringtail (Austrolestes annulosus), a damselfly (Zygoptera: Lestidae)
Dragonfly (top) and damselfly (bottom) wing shape and venation
Damselflies in copulatory "wheel"
Ovipositing flight of two azure damselfly couples (Coenagrion puella)
A pair of Ceriagrion cerinorubellum mating
Onychogomphus forcipatus male
Libellula depressa resting
Nymph
Anax imperator in flight

Odonata is an order of flying insects that includes the dragonflies and damselflies.

The nymphs grow and molt, usually in dusk or dawn, into the flying teneral immature adults, whose color is not yet developed.

Grasshopper

Fossil grasshoppers at the Royal Ontario Museum
Ensifera, like this great green bush-cricket Tettigonia viridissima, somewhat resemble grasshoppers but have over 20 segments in their antennae and different ovipositors.
Structure of mouthparts
Frontal view of Egyptian locust (Anacridium aegyptium) showing the compound eyes, tiny ocelli and numerous setae
Six stages (instars) of development, from newly hatched nymph to fully winged adult
Romalea microptera grasshoppers: female (larger) is laying eggs, with male in attendance.
Millions of plague locusts on the move in Australia
Cottontop tamarin monkey eating a grasshopper
Grasshopper with parasitic mites
Locusts killed by the naturally occurring fungus Metarhizium, an environmentally friendly means of biological control. CSIRO, 2005
Detail of grasshopper on table in Rachel Ruysch's painting Flowers in a Vase, c. 1685. National Gallery, London
Sir Thomas Gresham's gilded grasshopper symbol, Lombard Street, London, 1563
Fried grasshoppers from Gunung Kidul, Yogyakarta, Indonesia
Sweet-and-salty grasshoppers dish in Japan (Inago no Tsukudani)
Crop pest: grasshopper eating a maize leaf
Egyptian hieroglyphs "snḥm"
A grasshopper beam engine, 1847
Gaudy grasshopper, Atractomorpha lata, evades predators with camouflage.
Lubber grasshopper, Titanacris albipes, has deimatically coloured wings, used to startle predators.
Leaf grasshopper, Phyllochoreia ramakrishnai, mimics a green leaf.
Painted grasshopper, Dactylotum bicolor, deters predators with warning coloration.
Spotted grasshopper, Aularches miliaris, defends itself with toxic foam and warning colours.<ref>{{cite journal |author=Hingston, R.W.G. | year=1927 |doi=10.1111/j.1365-2311.1927.tb00060.x |title=The liquid-squirting habit of oriental grasshoppers| journal=Transactions of the Entomological Society of London |volume=75 |pages=65–69}}</ref>

Grasshoppers are a group of insects belonging to the suborder Caelifera.

As hemimetabolous insects, they do not undergo complete metamorphosis; they hatch from an egg into a nymph or "hopper" which undergoes five moults, becoming more similar to the adult insect at each developmental stage.

Cricket (insect)

African field cricket, Gryllus bimaculatus
A male Gryllus cricket chirping: Its head faces its burrow; the leathery fore wings (tegmina; singular "tegmen") are raised (clear of the more delicate hind wings) and are being scraped against each other (stridulation) to produce the song. The burrow acts as a resonator, amplifying the sound.
Two adult domestic crickets, Acheta domesticus, feeding on carrot
Various instars of Gryllus assimilis, by Robert Evans Snodgrass, 1930
Crickets are reared as food for pets and zoo animals like this baboon spider, Pterinochilus murinus, emerging from its den to feed.
Fossil cricket from the Cretaceous of Brazil
Il Grillo Parlante (The Talking Cricket) illustrated by Enrico Mazzanti for Carlo Collodi's 1883 children's book "Le avventure di Pinocchio" (The Adventures of Pinocchio)
Illustration for Charles Dickens's 1883 Cricket on the Hearth by Fred Barnard
Meiji period cricket holder in the form of a norimono palanquin, c. 1850
Deep-fried house crickets (Acheta domesticus) at a market in Thailand
Jiminy Cricket, from Walt Disney's movie Pinocchio (1940)

Crickets are orthopteran insects which are related to bush crickets, and, more distantly, to grasshoppers.

Crickets are hemimetabolic insects, whose lifecycle consists of an egg stage, a larval or nymph stage that increasingly resembles the adult form as the nymph grows, and an adult stage.