haemocoel, an arthropod's internal cavity, accommodates its interior
organs, and through which its
haemolymph – analogue of
blood – circulates; it has an
open circulatory system. Like their exteriors, the internal organs of arthropods are generally built of repeated segments. Their
nervous system is "ladder-like", with paired
ventralnerve cords running through all segments and forming paired
ganglia in each segment. Their heads are formed by fusion of varying numbers of segments, and their
brains are formed by fusion of the ganglia of these segments and encircle the
excretory systems of arthropods vary, depending as much on their environment as on the
subphylum to which they belong.
Arthropods use combinations of
compound eyes and pigment-pit
ocelli for vision. In most species, the ocelli can only detect the direction from which light is coming, and
the compound eyes are the main source of information, but the main eyes of
spiders are ocelli that can form images and, in a few cases, can swivel to track prey. Arthropods also have a wide range of chemical and mechanical sensors, mostly based on modifications of the many bristles known as
setae that project through their cuticles. Similarly, their reproduction and development are varied; all terrestrial species use
internal fertilization, but this is sometimes by indirect transfer of the sperm via an appendage or the ground, rather than by direct injection. Aquatic species use either internal or
external fertilization. Almost all arthropods lay eggs, but many species give birth to live young after the eggs have hatched inside the mother, and a few are genuinely
viviparous, such as
aphids. Arthropod hatchlings vary from miniature adults to grubs and
caterpillars that lack jointed limbs and eventually undergo a total
metamorphosis to produce the adult form. The level of maternal care for hatchlings varies from nonexistent to the prolonged care provided by
The evolutionary ancestry of arthropods dates back to the
Cambrian period. The group is generally regarded as
monophyletic, and many analyses support the placement of arthropods with
cycloneuralians (or their constituent clades) in a superphylum
Ecdysozoa. Overall, however, the
basal relationships of animals are not yet well resolved. Likewise, the relationships between various arthropod groups are still actively debated. Today, Arthropods contribute to the human food supply both directly as food, and more importantly indirectly as
pollinators of crops. Some species are known to spread severe disease to humans,
livestock, and crops. (Full article...)
Yantaromyrmex is an
ants first described in 2013. Members of this genus are in the subfamily
Dolichoderinae of the family
Formicidae, known from
Middle Eocene to
Early Oligocene fossils found in
Europe. The genus currently contains five described species, Y. constrictus, Y. geinitzi, Y. intermedius, Y. mayrianum and Y. samlandicus. The first specimens were collected in 1868 and studied by Austrian entomologist
Gustav Mayr, who originally placed the fossils in other ant genera until the fossils were reviewed and subsequently placed into their own genus. These ants are small, measuring from 4 to 6 mm (0.16 to 0.24 in) in length and can be characterized by their trapezoidal shaped head-capsules and oval compound eyes that are located slightly to the rear of the capsules midpoint, with no known
ocelli present. (Full article...)
The head of a small white butterfly (Pieris rapae). Note the upward pointing labial palpi on both sides of the coiled proboscis.
The external morphology of Lepidoptera is the
physiological structure of the bodies of
insects belonging to the order
Lepidoptera, also known as
moths. Lepidoptera are distinguished from other orders by the presence of
scales on the external parts of the body and appendages, especially the wings. Butterflies and moths vary in size from
microlepidoptera only a few millimetres long, to a wingspan of many inches such as the
Atlas moth. Comprising over 160,000 described species, the Lepidoptera possess variations of the basic body structure which has evolved to gain advantages in adaptation and distribution.
The adult body has a hardened
exoskeleton, except for the abdomen which is less sclerotised. The head is shaped like a capsule with appendages arising from it. Adult mouthparts include a prominent
proboscis formed from maxillary
galeae, and are adapted for sucking nectar. Some species do not feed as adults, and may have reduced mouthparts, while others have them modified for piercing and suck blood or fruit juices.
Mandibles are absent in all except the
Micropterigidae which have
chewing mouthparts. Adult Lepidoptera have two immobile, multi-faceted
compound eyes, and only two
simple eyes or ocelli, which may be reduced. The three segments of the
thorax are fused together.
Antennae are prominent and besides the faculty of smell, also aid navigation, orientation, and balance during flight. In moths, males frequently have more feathery antennae than females, for detecting the female
pheromones at a distance. There are two pairs of
membranouswings which arise from the mesothoracic (middle) and metathoracic (third) segments; they are usually completely covered by minute
scales. The two wings on each side act as one by virtue of
wing-locking mechanisms. In some groups, the females are flightless and have reduced wings. The abdomen has ten segments connected with movable inter-segmental membranes. The last segments of the abdomen form the external
genitalia. The genitalia are complex and provide the basis for family identification and species discrimination. (Full article...)
Horse-flies or horseflies are true
flies in the family Tabanidae in the
insectorderDiptera. They are often large and agile in flight, and the females bite animals, including humans, to
obtain blood. They prefer to fly in sunlight, avoiding dark and shady areas, and are inactive at night. They are found all over the world except for some islands and the polar regions (Hawaii, Greenland, Iceland). Both horse-flies and
botflies (Oestridae) are sometimes referred to as gadflies.
Adult horse-flies feed on nectar and plant
exudates; the males have weak
mouthparts and only the females bite animals to obtain enough
protein from blood to produce
eggs. The mouthparts of females are formed into a stout stabbing organ with two pairs of sharp cutting blades, and a spongelike part used to lap up the blood that flows from the wound. The larvae are
predaceous and grow in semiaquatic habitats.
The Colorado potato beetle (Leptinotarsa decemlineata), also known as the Colorado beetle, the ten-striped spearman, the ten-lined potato beetle, or the potato bug, is a major
potato crops. It is about 10 mm (3⁄8 in) long, with a bright yellow/orange body and five bold brown stripes along the length of each of its
elytra. Native to the
Rocky Mountains, it spread rapidly in potato crops across
America and then
Europe from 1859 onwards. (Full article...)
These ants are known to be an ecologically dominant and important group of ants, but they are sometimes regarded as pests because they disturb soil and enter human houses. Farmers in rural Australia place animal carcasses on meat ant (I. purpureus) mounds as a method of disposing of them; meat ants consume the carcass and reduce it to bones in a matter of weeks. Meat ants also engage in ritualised fighting, which helps prevent casualties and solve territorial disputes between neighbouring colonies. The largest members of this genus are those of the I. purpureus species group, measuring 8 mm (0.31 in).
nuptial flight, queen ants may establish a colony by themselves, by budding, or cooperatively, where a subset of the colony migrates to a new location or when multiple queens help find a suitable nesting spot, but they display intolerance to each other when workers are present. The eggs take 44 to 61 days to fully develop into adults. Ants of the genus live in a wide variety of habitats and nest in soil in numbers that range from a few hundred individuals to over 300,000 in a single colony. Depending on the species, nests are large mounds covered in pebbles with multiple entrances, while others live above ground in twig nests. In some cases, ants dwell in several nest sites connected by paths; some of these nests can extend to 650 m (2,130 ft) in length. Some species associate with caterpillars and butterflies that provide the ants with secretions and
honeydew, and I. bicknelli pollinates
orchids. These ants are predators and scavengers; they hunt for prey to feed their young. Notably, these ants are immune to the toxins of the
cane toad and feed on the juveniles. Predators such as spiders, birds, lizards, and other ants prey on Iridomyrmex ants. (Full article...)
B. clavata holotype
Brownimecia is an
ants, the only genus in the
tribeBrownimeciini and subfamily Brownimeciinae of the
Formicidae. Fossils of the single identified species, Brownimecia clavata, are known from the
Middle Cretaceous of North America. The genus is one of several ants described from Middle Cretaceous
New Jersey. Brownimecia was initially placed in the subfamily
Ponerinae, until it was transferred to its own subfamily in 2003; it can be distinguished from other ants due to its unusual
sickle-like mandibles and other morphological features that makes this ant unique among the Formicidae. The ant is also small, measuring 3.43 millimetres (0.135 in), and a stinger is present in almost all of the specimens collected. The morphology of the mandibles suggest a high level of feeding specialization. (Full article...)
Bees are found on every continent except for
Antarctica, in every habitat on the planet that contains insect-pollinated
flowering plants. The most common bees in the
Northern Hemisphere are the
Halictidae, or sweat bees, but they are small and often mistaken for wasps or flies. Bees range in size from tiny
stingless bee species, whose workers are less than 2 millimetres (0.08 in) long, to Megachile pluto, the largest species of leafcutter bee, whose females can attain a length of 39 millimetres (1.54 in).
Caprella mutica, commonly known as the Japanese skeleton shrimp, is a
skeleton shrimp. They are relatively large
caprellids, reaching a maximum length of 50 mm (2.0 in). They are
sexually dimorphic, with the males usually being much larger than the females. They are characterized by their "hairy" first and second
thoracic segments and the rows of spines on their bodies. Body color ranges from green to red to blue, depending on the environment. They are
omnivorous highly adaptable opportunistic feeders. In turn, they provide a valuable food source for
crabs, and other larger
predators. They are usually found in dense colonies attached to submerged man-made structures, floating
seaweed, and other organisms.
C. mutica are
native to shallow protected bodies of water in the
Sea of Japan. In as little as 40 years, they have become an
invasive species in the
North Pacific, and along the coasts of
New Zealand. They are believed to have been accidentally introduced to these areas through the global maritime traffic and aquaculture. Outside of their native range, C. mutica are often exclusively
synanthropic, being found in large numbers in and around areas of human activity. Their ecological and economic impact as an invasive species is unknown, but they pose a serious threat to native populations of skeleton shrimp in the affected areas. (Full article...)
spiders have been depicted in popular culture, mythology and in symbolism. From
Greek mythology to
African folklore, the spider has been used to represent a variety of things, and endures into the present day with characters such as
Shelob from The Lord of the Rings and
Spider-Man from the eponymous comic series. It is also a symbol of mischief and malice for its toxic venom and the slow death it causes, which is often seen as a curse. In addition, the spider has inspired creations from an ancient
geoglyph to a modern
steampunkspectacle. Spiders have been the
focus of fears, stories and mythologies of various cultures for centuries.
The spider has symbolized patience and persistence due to its hunting technique of setting
webs and waiting for its prey to become ensnared. Numerous cultures attribute the spider's ability to spin webs with the origin of
net making. Spiders are associated with creation myths because they seem to weave their own artistic worlds. Philosophers often use the spider's web as a
analogy, and today terms such as the Internet or World Wide Web evoke the inter-connectivity of a spider web. (Full article...)
Females have a body length of about 8 mm while males tend to be slightly smaller. The length of the spider's legs are on average 5 or 6 times the length of its body. Pholcus phalangioides has a habit of living on the ceilings of rooms, caves, garages or cellars.
This spider species is considered beneficial in parts of the world because it preys on other spiders, including species considered dangerous such as
redback spiders. However, when living in human buildings, it will primarily attack, kill and eradicate native spider species and, therefore, this invasive spider species has already been considered as very dangerous for the native spider fauna. Pholcus phalangioides is known to be harmless to humans and a potential for the medicinal use of their webs has been reported. (Full article...)
Interpretive drawing of PIN 1271/2, the holotype of Dvulikiaspis menneri
prosoma (head) was subquadrate (almost square) to parabolic (nearly U-shaped), with (bean-shaped) to subovate (nearly oval)
eyes and surrounded by a marginal rim. The
abdomen was composed by a fused buckler and a postabdomen that occupied most of the body length. The
appendages (limbs) were uniform. The sixth and last pair of them had a paddle-like shape and was placed in front of the midpoint of the prosoma. The largest specimen was 2.64 centimetres (1.04 inches) long.
The first fossil was described in 1959 as a new species of the
eurypteridStylonurus, while the other two were discovered in 1974. It would not be until 2014 when D. menneri was recognized as a chasmataspidid genus, being placed in the
familyDiploaspididae. However, Dvulikiaspis was similar to Loganamaraspis and especially Hoplitaspis, with which it could form a new separate family of chasmataspidids. (Full article...)
Myrmecia inquilina is a species of ant
Australia in the subfamily
Myrmeciinae, first discovered in 1955 and described by Athol Douglas and William Brown Jr. in 1959. These ants are large, measuring 21.4
in). During the time of its discovery, Douglas and Brown announced M. inquilina as the first
social parasite among the primitive subfamilies, and today it is one of the two known Myrmecia species to have no worker caste. Two host species are known, Myrmecia nigriceps and Myrmecia vindex. Aggression between M. inquilina and its host species does not occur, and colonies may only produce M. inquilina brood months after the inquiline queens begin to lay their eggs. Queens eat the colony brood or
trophic eggs, and other Myrmecia species may kill M. inquilina queens if they reject them. Due to its restricted distribution and threats to its habitat, the ant is "
vulnerable" according to the
IUCN Red List. (Full article...)
Fossil claw of Jaekelopterus howelli. The massive claws of the pterygotids are their primary distinguishing feature.
One of the most successful groups of eurypterids, the pterygotids were the only eurypterid family to achieve a truly
worldwide distribution. Several evolutionary innovations made the pterygotids unique among the eurypterids, with large and flattened
telsons (the posteriormost segment of the body) likely used as rudders to provide additional agility and enlarged
chelicerae (frontal appendages) with claws. These claws were robust and possessed teeth which would have made many members of the group formidable predators. The strange proportions and large size of the pterygotid eurypterids led to the quarrymen who discovered the very first fossil remains of the group to give them the
common name "
Studies on the cheliceral morphology and compound eyes of the pterygotids have revealed that the members of the group, despite overall morphological similarities, were highly divergent in their ecological roles. Pterygotid ecology ranged from generalized predatory behaviour in basal members of the group, such as Erettopterus, to active apex predators, such as Jaekelopterus and Pterygotus, and ambush predators and scavengers, such as Acutiramus. (Full article...)
Misumena vatia is a
crab spider with a
holarctic distribution. In North America, it is called the goldenrod crab spider or flower (crab) spider, as it is commonly found hunting in
goldenrod sprays and
milkweed plants. They are called crab spiders because of their unique ability to walk sideways as well as forwards and backwards. Both males and females of this species progress through several molts before reaching their adult sizes, though females must molt more to reach their larger size. Females can grow up to 10 mm (0.39 in) while males are quite small, reaching 5 mm (0.20 in) at most. Misumena vatia are yellow or white, and have the ability to change between these two colors based on their surroundings. They have a complex visual system, with eight eyes, that they rely on for prey capture and for their color-changing abilities. Sometimes, if Misumena vatia consume colored prey, the spider itself will take on that color.
Misumena vatia feed on common insects, often consuming prey much larger than themselves. They use venom to immobilize their prey, though they are harmless to humans. They face threats due to parasites and larger insects. For Misumena vatia, survival depends on the choice of hunting site. The spiders closely monitor multiple sites to see if others nearby are frequented by greater numbers of potential prey. The primary
sex ratio is biased toward females. Females are stationary and choose a flower to settle on while males cover great distances searching for mates. Females do not emit pheromones, rather, they leave "draglines" of silk behind them as they move, which males follow. Females live longer than males, on average. After mating, females guard their nests until the young have hatched, after which they die. (Full article...)
macro view of a Gonia capitatafly feeding on
honey, showing its
pedipalps (the two appendages protruding from the proboscis), two types of insect mouthparts. The proboscis actually comprises the labium, a quadrupedal structure, and a sponge-like labellum at the end. Flies eat solid food by secreting
saliva and dabbing it over the food item. As the saliva dissolves the food, the solution is then drawn up into the mouth as a liquid. The labellum's surface is covered by minute food channels which form a tube leading to the
esophagus, and food is drawn up the channels by
The Ozyptila praticola species of
crab spider is found throughout
Europe and the
Middle East. They do not build webs to trap prey, but are active hunters. Crab spiders are so named because of their first two pairs of legs, which are held out to the side giving them a
crab-like appearance. Also, like crabs, these spiders move sideways and backwards more easily than forwards.
The Painted Lady (Vanessa cardui) is a well-known colourful
butterfly, found on every continent except
Antarctica. It occurs in any
temperate zone, including mountains in the
tropics. The species is resident only in warmer areas, but migrates in spring, and sometimes again in autumn.
The orb-weaver spiders (family Araneidae) are the familiar builders of spiral wheel-shaped webs often found in gardens, fields and forests. The family is a large one, including over 2800
species in over 160
genera worldwide, making it the third largest known (behind Salticidae and Linyphiidae). The web has always been thought of as an engineering marvel.
Compound eyes on a
blue bottle fly. Unlike simple eyes, which have a single concave photoreceptive surface, compound eyes consist of a number of individual lenses (called
ommatidia) laid out on a convex surface; this means that they point in slightly different directions. Compound eyes provide a wide
field of view and can detect fast movement, but have low resolution.
A mole cricket, an
insect belonging to the Gryllotalpidaefamily. Mole crickets are common insects, found on every continent except
Antarctica, but because they are
nocturnal and spend nearly all their lives underground in extensive tunnel systems, they are rarely seen. This specimen is likely to be Gryllotalpa brachyptera and is about 3.5 cm (1.4 in.) in size.
The western honey bee (Apis mellifera) is the most common of the 7–12 species of
honey bee worldwide. It is believed to have originated in either Africa or Asia, and spread naturally through Africa, the Middle East and Europe. Following human introduction into the Americas and Oceania, the species is now found on every continent except Antarctica. Humans have been collecting
honey from bees for thousands of years, with evidence in the form of
rock art found in France and Spain, dating to around 7000 BC. Along with other insects, the honey bee is an important
pollinator, with a large number of the
crop species farmed worldwide depending on it.
The Globe Skimmer (Pantala flavescens) is the most widespread
dragonfly species on the planet, found between about the 40th
parallels of latitude, or where the annual mean temperature is above 20 °C (68 °F), except in
Europe where there are only occasional sightings.
The head and mandibles of an
Insect mandibles grasp, crush, or cut the insect’s food, or defend against predators or rivals. These mandibles move in the horizontal plane unlike those of the
compound eye is a visual
organ found in certain
arthropods. The compound eye consists of between 12 and 1,000
ommatidia, little dark/bright sensors. The image perceived by the arthropod is "recalculated" from the numerous ommatidia which point in slightly different directions. In contrast to other
eye types, there is no central
retina. Though the resulting image is poor in resolution, it can detect quick movements and, in some cases, the
polarization of light.
Dragonflies have about 30,000 facets to their compound eyes, giving them nearly a 360° field of vision.
An assassin bug belonging to the Reduviidae family of insects. A
predatory insect so named because of its tendency to wait in
ambush for its prey, the assassin bug uses its long
rostrum to inject a lethal
saliva that liquefies the internal structures of the prey, which are then sucked out.
The rose chafer (Cetonia aurata) is a reasonably large
beetle (20 mm/¾ in long) that has metallic green coloration with a distinct V shaped
scutellum, the small triangular area between the wing cases just below the
thorax. Rose chafers are found over southern and central Europe and the southern part of the UK.
A Eusthenia species of stonefly. The
order contains almost 3,500 known species, including the only known insects that are exclusively aquatic from birth to death. Stoneflies are believed to be one of the most primitive groups of
Neoptera and are found worldwide, with the exception of
Expand an existing article. Existing articles are often incomplete and missing information on key aspects of the topic. It is particularly important that the most widely read articles be broad in their scope.
Wikipedia:WikiProject Arthropods/Popular pages (updated monthly) shows the number of views each article gets, along with assessments of its quality and importance. Articles with higher importance ratings and greater numbers of views are the priority for article improvements, but almost all our articles would benefit from expansion.
Stubs can be found in
Category:Arthropod stubs and its subcategories.