A report on Arthropod

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

Arthropods (, (gen.

- Arthropod

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


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

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

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.
Insect morphology 
A- Head B- Thorax C- Abdomen
Basic motion of the insect wing in insect with an indirect flight mechanism scheme of dorsoventral cut through a thorax segment with a wings, b joints, c dorsoventral muscles, d longitudinal muscles.

They are the largest group within the arthropod phylum.


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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

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.


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Formation of anterior segments across arthropod taxa based on gene expression and neuroanatomical observations, Note the chelicera(Ch) and chelifore(Chf) arose from somite 1 and thus correspond to the first antenna(An/An1) of other arthropods.
Female scorpion Compsobuthus werneri carrying its young (white)
A microscopic mite Lorryia formosa.

The subphylum Chelicerata (from New Latin,, ) constitutes one of the major subdivisions of the phylum Arthropoda.


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Basic characteristics of arachnids include four pairs of legs (1) and a body divided into two tagmata: the cephalothorax (2) and the abdomen (3)
"Arachnida" from Ernst Haeckel's Kunstformen der Natur, 1904
Hubbardia pentapeltis (Schizomida)
Fossil Goniotarbus angulatus (Phalangiotarbi)
Fossil of Kreischeria (Trigonotarbida)
Eukoenenia spelaea (Palpigradi)

Arachnida is a class of joint-legged invertebrate animals (arthropods), in the subphylum Chelicerata.


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The head of Scutigera coleoptrata, showing antennae, compound eyes and mouthparts
Scolopendra cingulata, a centipede
Tachypodoiulus niger, a millipede
Scutigerella immaculata, a symphylan
Pauropus huyxleyi, a pauropodan
Some of the various hypotheses of myriapod phylogeny. Morphological studies (trees a and b) support a sister grouping of Diplopoda and Pauropoda, while studies of DNA or amino acid similarities suggest a variety of different relationships, including the relationship of Pauropoda and Symphyla in tree c.

Myriapoda is a subphylum of arthropods containing millipedes, centipedes, and others.


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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

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

Diagram of biramous leg of a trilobite; Agnostus spp.

Arthropod leg

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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 arthropod leg is a form of jointed appendage of arthropods, usually used for walking.


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Underside of Scolopendra cingulata, showing the forcipules
Close-up of the tail-like rear pair of legs of a centipede
A representative millipede and centipede (not necessarily to scale)
A centipede protecting her first instar offspring
A centipede (Scolopendra cingulata) being eaten by a European roller
A juvenile centipede seen on vegetation at Agumbe, Karnataka, India
Centipedes at Wangfujing market
Man holding Scolopendra gigantea. Trinidad, 1961

Centipedes (from the New Latin prefix centi-, "hundred", and the Latin word pes, pedis, "foot") are predatory arthropods belonging to the class Chilopoda (Ancient Greek χεῖλος, kheilos, lip, and New Latin suffix -poda, "foot", describing the forcipules) of the subphylum Myriapoda, an arthropod group which also includes millipedes and other multi-legged creatures.


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Approximate relative diversity of extant millipede orders, ranging from ca. 3,500 species of Polydesmida to 2 species of Siphoniulida
Octoglena sierra (Colobognatha, Polyzoniida)
Anadenobolus monilicornis (Juliformia, Spirobolida)
Harpaphe haydeniana (Polydesmida)
Pauropods are thought to be the closest relative of millipedes.
A representative millipede and centipede (not necessarily to scale)
Representative body types of the Penicillata (top), Pentazonia (middle), and Helminthomorpha (bottom)
Anterior anatomy of a generalized helminthomorph millipede
Paranota of polydesmidan (left) and platydesmidan millipedes
A female Illacme plenipes with 618 legs (309 pairs)
Epibolus pulchripes mating; the male is on the right
Growth stages of Nemasoma (Nemasomatidae), which reaches reproductive maturity in stage V
A Sceliages beetle transporting a millipede carcass
Ammodesmus nimba from Guinea, West Africa, curled in a defensive coil
Psammodesmus bryophorus camouflaged with symbiotic mosses
Giant fire millipede (Aphistogoniulus corallipes), Madagascar
Spotted snake millipedes can be agricultural pests.
Flat millipede found in the Mount Cameroon Forest

Millipedes are a group of arthropods that are characterised by having two pairs of jointed legs on most body segments; they are known scientifically as the class Diplopoda, the name derived from this feature.

Large antennae on a longhorn beetle

Antenna (biology)

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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.