Antenna (biology)

Large antennae on a longhorn beetle
Cutaway diagram of a barnacle, with antennae highlighted by arrow
Terms used to describe shapes of insect antennae
Antennal shape in the Lepidoptera from C. T. Bingham (1905)
Electron micrograph of antenna surface detail of a wasp (Vespula vulgaris)
Olfactory receptors (scales and holes) on the antenna of the butterfly Aglais io, electron micrograph

Antennae ( antenna), sometimes referred to as "feelers", are paired appendages used for sensing in arthropods.

- Antenna (biology)

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Ants are eusocial insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera.

Ants fossilised in Baltic amber
Diagram of a worker ant (Neoponera verenae)
Bull ant showing the powerful mandibles and the relatively large compound eyes that provide excellent vision
Ant head
Seven leafcutter ant workers of various castes (left) and two queens (right)
Meat eater ant nest during swarming
Alate male ant, Prenolepis imparis
Honey ants (Prenolepis imparis) mating
Fertilised meat-eater ant queen beginning to dig a new colony
Two Camponotus sericeus workers communicating through touch and pheromones
A Plectroctena sp. attacks another of its kind to protect its territory.
A weaver ant in fighting position, mandibles wide open
Ant mound holes prevent water from entering the nest during rain.
Two Weaver ants walking in tandem.
Leaf nest of weaver ants, Pamalican, Philippines
Myrmecocystus, honeypot ants, store food to prevent colony famine.
An ant trail
Meat-eater ants feeding on a cicada: social ants cooperate and collectively gather food
A worker Harpegnathos saltator (a jumping ant) engaged in battle with a rival colony's queen (on top)
The spider Myrmarachne plataleoides (female shown) mimics weaver ants to avoid predators.
An ant collects honeydew from an aphid
Ants may obtain nectar from flowers such as the dandelion, but are only rarely known to pollinate flowers.
A meat ant tending a common leafhopper nymph
Spiders (Like this Menemerus jumping spider) sometimes feed on ants
Weaver ants are used as a biological control for citrus cultivation in southern China.
Roasted ants in Colombia
Ant larvae for sale in Isaan, Thailand
The tiny pharaoh ant is a major pest in hospitals and office blocks; it can make nests between sheets of paper.
Camponotus nearcticus workers travelling between two formicaria through connector tubing
Aesop's ants: illustration by Milo Winter, 1888–1956
An ant pictured in the coat of arms of Multia

They are easily identified by their geniculate (elbowed) antennae and the distinctive node-like structure that forms their slender waists.


One of three orders of non-insect hexapods within the class Entognatha (alongside Collembola (springtails) and Protura).

A dipluran of the family Campodeidae
Anatomy of Campodea (Campodeidae) and Japyx (Japygidae)

Diplurans have long antennae with 10 or more bead-like segments projecting forward from the head.


Type of arthropod constituting the subclass Cirripedia in the subphylum Crustacea, and is hence related to crabs and lobsters.

Whale barnacles attached to the throat of a humpback whale
Nauplius larva of Elminius modestus
Nauplius larva of a barnacle with fronto-lateral horns
"Cirripedia" from Ernst Haeckel's Kunstformen der Natur (1904): The crab at the centre is nursing the externa of the parasitic cirripede Sacculina.
Barnacles and limpets compete for space in the intertidal zone
Goose barnacles, with their cirri extended for feeding
Underside of large Chesaconcavus sp. (Miocene) showing internal plates in bioimmured smaller barnacles
Balanus improvisus, one of the many barnacle taxa described by Charles Darwin
Miocene (Messinian) Megabalanus, smothered by sand and fossilised
Chesaconcavus, a Miocene barnacle from Maryland
Barnacles attached to pilings along the Siuslaw River in Oregon
Goose barnacles in a restaurant in Madrid

Free-living barnacles are attached to the substratum by cement glands that form the base of the first pair of antennae; in effect, the animal is fixed upside down by means of its forehead.

Arthropod leg

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.

They have paired appendages on some other segments, in particular, mouthparts, antennae and cerci, all of which are derived from paired legs on each segment of some common ancestor.


External body part, or natural prolongation, that protrudes from an organism's body.

A beetle leg

In invertebrate biology, an appendage refers to any of the homologous body parts that may extend from a body segment, including antennae, mouthparts (including mandibles, maxillae and maxillipeds), gills, locomotor legs (pereiopods for walking, and pleopods for swimming), sexual organs (gonopods), and parts of the tail (uropods).


The family Scarabaeidae, as currently defined, consists of over 30,000 species of beetles worldwide; they are often called scarabs or scarab beetles.

On this high quality closeup, head anatomic details are well visible.
Sacred scarab in a cartouche of Thutmosis III from Karnak temple of Amun-Ra, Egypt
A scarab beetle grub from Australia.

Scarabs are stout-bodied beetles, many with bright metallic colours, measuring between 1.5 and 160 mm. They have distinctive, clubbed antennae composed of plates called lamellae that can be compressed into a ball or fanned out like leaves to sense odours.

Crustacean larva

Crustaceans may pass through a number of larval and immature stages between hatching from their eggs and reaching their adult form.

Close-up of an adult Triops (Notostraca), showing the naupliar eye between the two compound eyes
A nauplius of Euphausia pacifica hatching, emerging backwards from the egg
Eggs being brooded by a female Orconectes obscurus crayfish: such large eggs are often indicative of abbreviated development.
Zoea larva of a European lobster
A phyllosoma larva of the spiny lobster Palinurus elephas, from Ernst Haeckel's Kunstformen der Natur
First chalimus of Lepeophtheirus elegans Gusev, 1951 (Copepoda, Caligidae):
 A, leg 3;
 B, leg 3 (other specimen);
 C, leg 4;
 D, caudal ramus;
 E, habitus of putative female, dorsal.
 Scale bars: A–D = 0.025 mm; E = 0.2 mm.

Each head segment has a pair of appendages; the antennules, antennae, and mandibles.


Crustaceans (Crustacea ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp.

A shed carapace of a lady crab, part of the hard exoskeleton
Body structure of a typical crustacean – krill
Abludomelita obtusata, an amphipod
Eggs of Potamon fluviatile, a freshwater crab
Zoea larva of the European lobster, Homarus gammarus
Copepods, from Ernst Haeckel's 1904 work Kunstformen der Natur
Decapods, from Ernst Haeckel's 1904 work Kunstformen der Natur
Eryma mandelslohi, a fossil decapod from the Jurassic of Bissingen an der Teck, Germany
Norway lobsters on sale at a Spanish market

Each somite, or body segment can bear a pair of appendages: on the segments of the head, these include two pairs of antennae, the mandibles and maxillae; the thoracic segments bear legs, which may be specialised as pereiopods (walking legs) and maxillipeds (feeding legs).


Arthropods (, (gen.

Structure of a biramous appendage.
Alignment of anterior body segments and appendages across various arthropod taxa, based on the observations until mid 2010s. Head regions in black.
Illustration of an idealized arthropod exoskeleton.
Cicada climbing out of its exoskeleton while attached to tree
Arthropod eyes
Head of a wasp with three ocelli (center), and compound eyes at the left and right
Compsobuthus werneri female with young (white)
The nauplius larva of a penaeid shrimp
Marrella, one of the puzzling arthropods from the Burgess Shale
The velvet worm (Onychophora) is closely related to arthropods
Insects and scorpions on sale in a food stall in Bangkok, Thailand

In some segments of all known arthropods the appendages have been modified, for example to form gills, mouth-parts, antennae for collecting information, or claws for grasping; arthropods are "like Swiss Army knives, each equipped with a unique set of specialized tools."


Largest of the six classes of crustaceans, containing about 40,000 living species, divided among 16 orders.

Leptostraca such as Nebalia bipes retain the primitive condition of having seven abdominal segments.
Grapsus grapsus, a terrestrial crab
Squilla empusa, a mantis shrimp
Odontodactylus scyllarus (Hoplocarida: Stomatopoda)
Porcellio scaber and Oniscus asellus (Peracarida: Isopoda)
Cancer pagurus (Eucarida: Decapoda)

The head bears two pairs of antennae, the first of which is often biramous (branching into two parts) and the second pair bear exopods (outer branches) which are often flattened into antennal scales known as scaphocerites.