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...)
Damselflies are flying insects of the suborder Zygoptera in the order Odonata. They are similar to dragonflies (which constitute the other odonatan suborder, Anisoptera) but are usually smaller and have slimmer bodies. Most species fold the wings along the body when at rest, unlike dragonflies which hold the wings flat and away from the body. Damselflies have existed since the Late Jurassic, and are found on every continent except Antarctica.
All damselflies are predatory insects; both nymphs and adults actively hunt and eat other insects. The nymphs are aquatic, with different species living in a variety of freshwater habitats including acidic bogs, ponds, lakes and rivers. The nymphs moult repeatedly, at the last moult climbing out of the water to undergo metamorphosis. The skin splits down the back, they emerge and inflate their wings and abdomen to gain their adult form. Their presence on a body of water indicates that it is relatively unpolluted, but their dependence on freshwater makes them vulnerable to damage to their wetland habitats.
Some species of damselfly have elaborate courtship behaviours. Many species are sexually dimorphic, the males often being more brightly coloured than the females. Like dragonflies, they reproduce using indirect insemination and delayed fertilisation. A mating pair form a shape known as a "heart" or "wheel", the male clasping the female at the back of the head, the female curling her abdomen down to pick up sperm from secondary genitalia at the base of the male's abdomen. The pair often remain together with the male still clasping the female while she lays eggs within the tissue of plants in or near water using a robust ovipositor. (Full article...)
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Black-headed sugar ant worker from Strangways, Victoria
The black-headed sugar ant (Camponotus nigriceps), also known as the brown sugar ant, is a species of Formicinaeant endemic to Australia. Found throughout most states, the species is a member of the genus Camponotus, a cosmopolitan genus of ants commonly known as carpenter ants. It was formally described and named by British entomologist Frederick Smith in 1858. These ants are characterised by their black head, reddish-brown mesosoma and black gaster, which can change in colour.
The species is polymorphic: workers and soldiers measure 6 to 12 millimetres (0.24 to 0.47 in) and males are 12 millimetres (0.47 in). The queens are the largest members of the colony, measuring 16 millimetres (0.63 in). Colonies dwell in dry regions, including open areas or in dry sclerophyll woodland, where they nest in soil, large mounds or under stones. Nuptial flight occurs in summer and nests can hold several thousand individuals. Considered a household pest, black-headed sugar ants feed on sweet foods and insects and tend to butterfly larvae. Numerous birds and fish prey on these ants. (Full article...)
Hughmilleriidae (the name deriving from the type genus Hughmilleria, which is named in honor of ScottishgeologistHugh Miller) is a family of eurypterids, an extinct group of aquatic arthropods. The hughmilleriids were the most basal members of the superfamily Pterygotioidea, in contrast with the more derived (more "advanced") families Pterygotidae and Slimonidae. Despite their classification as pterygotioids, the hughmilleriids possessed several characteristics shared with other eurypterid groups, such as the lanceolate telson (the most posterior segment of the body).
Hughmilleriids are defined as pterygotioid eurypterids with swimming legs similar to those of the type genus, Hughmilleria (that is, 7th and 8th leg segments narrow and 9th segment very small), and whose second to fifth pair of appendages were spiniferous. Some further diagnostic characters unite the group, such as the slightly enlarged chelicerae (frontal appendages) and the streamlined shape of their bodies. The family contains only two genera, Hughmilleria and Herefordopterus, though other genera have been referred to the family in the past, such as genera now considered part of families such as the Mycteroptidae and the Waeringopteridae.
The hughmilleriids were the most basal group of pterygotioid eurypterids, lacking the derived features that would come to evolve in the Slimonidae and Pterygotidae, such as flattened and expanded telsons (the posteriormost segment of the body, this feature is shared by both derived families) and enlarged cheliceral claws (exclusive to the pterygotids). In spite of the great similarity of both genera, Herefordopterus had derived characteristics that suggest a close relationship with Slimonidae and Pterygotidae, such as the marginal ornamentation of the telson. On the other hand, Hughmilleria had certain resemblance to the basal adelophthalmidEysyslopterus, sharing a triangular anterior carapace margin, possibly a plesiomorphic (of a common ancestor) trait. (Full article...)
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Adult female red back spider
The redback spider (Latrodectus hasselti), also known as the Australian black widow, is a species of highly venomous spider believed to originate in South Australia or adjacent Western Australian deserts, but now found throughout Australia, Southeast Asia and New Zealand, with colonies elsewhere outside Australia. It is a member of the cosmopolitan genus Latrodectus, the widow spiders. The adult female is easily recognised by her spherical black body with a prominent red stripe on the upper side of her abdomen and an hourglass-shaped red/orange streak on the underside. Females usually have a body length of about 10 millimetres (0.4 in), while the male is much smaller, being only 3–4 mm (0.12–0.16 in) long.
Mainly nocturnal, the female redback lives in an untidy web in a warm sheltered location, commonly near or inside human residences. It preys on insects, spiders and small vertebrates that become ensnared in its web. It kills its prey by injecting a complex venom through its two fangs when it bites, before wrapping them in silk and sucking out the liquefied insides. Often, it first squirts its victim with what resembles 'superglue' from its spinnerets, immobilising the prey by sticking the victim's limbs and appendages to its own body. The redback spider then trusses the victim with silk. Once its prey is restrained, it is bitten repeatedly on the head, body and leg segments and is then hauled back to the redback spider's retreat. Sometimes a potentially dangerous victim can be left to struggle for hours until it is exhausted enough to approach safely. Male spiders and spiderlings often live on the periphery of the female spiders' web and steal leftovers. Other species of spider and parasitoid wasps prey on this species. The redback is one of a number of arachnids that usually display sexual cannibalism while mating.
After mating, sperm is stored in the spermathecae, organs of the female reproductive tract, and can be used up to two years later to fertilise several clutches of eggs. Each clutch averages 250 eggs and is housed in a round white silken egg sac. The redback spider has a widespread distribution in Australia, and inadvertent introductions have led to established colonies in New Zealand, the United Arab Emirates, Japan and greenhouses in Belgium. (Full article...)
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Fossil specimens of Waptia
Waptia is an extinctgenus of arthropod from the Middle Cambrian of North America. It grew to a length of 6.65 cm (3 in), and had a large bivalved carapace and a segmented body terminating into a pair of tail flaps. It was an active swimmer and likely a predator of soft-bodied prey. It is also one of the oldest animals with direct evidence of brood care. Waptia fieldensis is the only species classified under the genusWaptia, and is known from the Burgess ShaleLagerstätte of British Columbia, Canada. Specimens of Waptia are also known from the Spence Shale of Utah, United States.
Based on the number of individuals, Waptia fieldensis is the third most abundant arthropod from the Burgess Shale Formation, with thousands of specimens collected. It was among the first fossils found by the American paleontologistCharles D. Walcott in 1909. He described it in 1912 and named it after two mountains near the discovery site – Wapta Mountain and Mount Field.
Although it bears a remarkable resemblance to modern crustaceans, its taxonomic affinities were long unclear. A comprehensive redescription published in 2018 classified it a member of Hymenocarina (which contains numerous other bivalved arthropods) within Mandibulata. (Full article...)
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Myrmecia inquilina is a species of ant endemic to 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 millimetres (0.84 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...)
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Andreacarus voalavo is a parasiticmite found on the Malagasy rodent Voalavo gymnocaudus. First described in 2007, it is closely related to Andreacarus gymnuromys and Andreacarus eliurus, which are found on other Malagasy rodents. The length of the idiosoma, the main body, is 630 to 670 μm in females and 450 to 480 μm in males. Unlike A. eliurus, this species lacks distinct sternal glands (secretory organs) between two lyrifissures (sensory organs) on the lower part of the female body. The pilus dentilis, a sensory organ on the chelicera, is serrate, which distinguishes it from A. gymnuromys. Females of A. gymnuromys also have a less ornamented sternal shield (covering part of the underparts) and shorter setae (bristles) on the upperparts. (Full article...)
Ochetellus is a genus of ants first described by Steve Shattuck in 1992. He placed it in the subfamily Dolichoderinae of the family Formicidae. The ants in this genus are small and black in colour; workers measure 1.75 to 3 millimetres (0.07 to 0.12 in) in length, the males at around 1.6 millimetres (0.06 in) are smaller, and the queens are the largest, reaching 4 millimetres (0.16 in). There are seven described species and three described subspecies that mostly live in Australia in a wide variety of habitats, but some species are found in Asia. One species, Ochetellus glaber, has been introduced into New Zealand and the United States.
The colonies are found in rotten wood, in the ground, under rocks or stones and in urban areas. The ants are both diurnal and nocturnal and forage on trees, in low vegetation and into human homes, where they are regarded as pests. These ants eat a variety of foods, including fruits, insects, sucrose, nectar and bird feces. They visit various flowers and attend to a variety of butterfly larvae. The thorny devil, an Australian lizard, predominantly feeds on Ochetellus workers, and other ant species also prey on them. (Full article...)
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Yellow morph of J. lagostoma
Johngarthia lagostoma is a species of terrestrial crab that lives on Ascension Island and three other islands in the South Atlantic. It grows to a carapace width of 110 mm (4.3 in) on Ascension Island, where it is the largest native land animal. It exists in two distinct colour morphs, one yellow and one purple, with few intermediates. The yellow morph dominates on Ascension Island, while the purple morph is more frequent on Rocas Atoll. The species differs from other Johngarthia species by the form of the third maxilliped.
Johngarthia lagostoma lives in burrows among vegetation, at altitudes of up to 400 m (1,300 ft), emerging at night to feed on plant matter and occasionally on animals. From January to March there is an annual migration to the sea to release the planktoniclarvae. The species was first described (as Gecarcinus lagostoma) by Henri Milne-Edwards in 1837 from material sent to him by the naturalists Jean René Constant Quoy and Joseph Paul Gaimard, collected by the French ship Astrolabe. (Full article...)
Ypresiomyrma is an extinct genus of ants in the subfamily Myrmeciinae that was described in 2006. There are four species described; one species is from the Isle of Fur in Denmark, two are from the McAbee Fossil Beds in British Columbia, Canada, and the fourth from the Bol’shaya Svetlovodnaya fossil site in Russia. The queens of this genus are large, the mandibles are elongated and the eyes are well developed; a stinger is also present. The behaviour of these ants would have been similar to that of extant Myrmeciinae ants, such as solitary foraging for arthropod prey and never leaving pheromone trails. The alates were poor flyers due to their size, and birds and animals most likely preyed on these ants. Ypresiomyrma is not assigned to any tribe, and is instead generally regarded as incertae sedis within Myrmeciinae. However, some authors believe Ypresiomyrma should be assigned as incertae sedis within Formicidae. (Full article...)
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Insects are the only group of invertebrates that have evolved wings and flight. Insects first flew in the Carboniferous, some 300 to 350 million years ago, making them the first animals to evolve flight. Wings may have evolved from appendages on the sides of existing limbs, which already had nerves, joints, and muscles used for other purposes. These may initially have been used for sailing on water, or to slow the rate of descent when gliding.
Two insect groups, the dragonflies and the mayflies, have flight muscles attached directly to the wings. In other winged insects, flight muscles attach to the thorax, which make it oscillate in order to induce the wings to beat. Of these insects, some (flies and some beetles) achieve very high wingbeat frequencies through the evolution of an "asynchronous" nervous system, in which the thorax oscillates faster than the rate of nerve impulses.
With a body length of 54 cm (21 in), Megarachne was a medium-sized eurypterid. If the original identification as a spider had been correct, Megarachne would have been the largest known spider to have ever lived. Eurypterids such as Megarachne are often called "sea scorpions", but the strata in which Megarachne has been found indicates that it dwelled in freshwater and not in marine environments.
Megarachne was similar to other eurypterids within the Mycteropoidea, a rare group known primarily from South Africa and Scotland. The mycteropoids had evolved a specialized method of feeding referred to as sweep-feeding. This involved raking through the substrate of riverbeds in order to capture and eat smaller invertebrates. Despite only two specimens having been recovered, Megarachne represents the most complete eurypterid discovered in Carboniferous deposits in South America so far. Due to their fragmentary fossil record and similarities between the genera, some researchers have hypothesized that Megarachne and two other members of its family, Mycterops and Woodwardopterus, represent different developmental stages of a single genus. (Full article...)
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Fossil specimen of C. ventricosus
Ciurcopterus is a genus of eurypterid, an extinct group of aquatic arthropods. Fossils of Ciurcopterus have been discovered in deposits of Late Silurian age in North America. Classified as part of the family Pterygotidae, the genus contains two species, C. sarlei from Pittsford, New York and C. ventricosus from Kokomo, Indiana. The genus is named in honor of Samuel J. Ciurca, Jr., who has contributed significantly to eurypterid research by discovering a large amount of eurypterid specimens, including the four specimens used to describe Ciurcopterus itself.
Ciurcopterus is the most basal (primitive) known member of the Pterygotidae, and combined characteristics of more derived members of the family with features of close relatives of the group, such as Slimonia. Measuring 70 centimetres (28 inches) in length, Ciurcopterus was relatively large though smaller than many of the later members of its family, which would grow to become the largest known arthropods to have ever lived. (Full article...)
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Novomessor albisetosus worker specimen
Novomessor albisetosus, also known as the desert harvester ant, is a species of ant found in the United States and Mexico. A member of the genus Novomessor in the subfamily Myrmicinae, it was first described by Austrian entomologist Gustav Mayr in 1886. It was originally placed in the genus Aphaenogaster, but a recent phylogenetic study concluded that it is genetically distinct and should be separated. It is a medium-sized species, measuring 6 to 8.5 millimeters (0.2 to 0.3 in) and has a ferruginous body color. It can be distinguished from other Novomessor species by its shorter head and subparallel eyes.
Novomessor albisetosus is found in desert and woodland habitats, nesting underground or under stones. The ants are active during the morning and evening but not when it is midday or the middle of the night. They forage for foods such as insect pieces, plant tissues and fruit. They may forage individually but cooperate when transporting large food items. Army ants are known to prey on this species. Nuptial flights begin in June. Workers are considered matured when half of their time is spent outside. (Full article...)
... that Darwin's bark spider makes the longest known spider web(pictured), spanning distances of up to 25 metres (82 ft), using the toughest known biomaterial, that is ten times as tough as Kevlar?
Image 8Mature queen of a termite colony, showing how the unsclerotised cuticle stretches between the dark sclerites that failed to stretch as the abdomen grew to accommodate her ovaries (from Arthropod exoskeleton)
Image 9Decapods, from Ernst Haeckel's 1904 work Kunstformen der Natur (from Crustacean)
Image 10The house centipedeScutigera coleoptrata has rigid sclerites on each body segment. Supple chitin holds the sclerites together and connects the segments flexibly. Similar chitin connects the joints in the legs. Sclerotised tubular leg segments house the leg muscles, their nerves and attachments, leaving room for the passage of blood to and from the hemocoel (from Arthropod exoskeleton)
Image 11 This fully-grown robber crab has tough fabric forming its joints, delicate biomineralized cuticle over its sensory antennae, optic-quality over its eyes, and strong, calcite-reinforced chitin armouring its body and legs; its pincers can break into coconuts (from Arthropod exoskeleton)
Image 12Ghost crab, showing a variety of integument types in its exoskeleton, with transparent biomineralization over the eyes, strong biomineralization over the pincers, and tough chitin fabric in the joints and the bristles on the legs (from Arthropod exoskeleton)
Image 15Some 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. (from Myriapoda)
Image 16Body structure of a typical crustacean – krill (from Crustacean)
Image 20Formation 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. (from Chelicerata)
Image 24Reconstruction of Mollisonia plenovenatrix, the oldest known arthropod with confirmed chelicerae (from Chelicerata)
Image 25This Zoea-stage larva is hardly recognisable as a crab, but each time it sheds its cuticle it remodels itself, eventually taking on its final crab form (from Arthropod exoskeleton)
Image 31In honeypot antrepletes, the abdomens of the workers that hold the sugar solution grow vastly, but only the unsclerotised cuticle can stretch, leaving the unstretched sclerites as dark islands on the clear abdomen (from Arthropod exoskeleton)
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.
The head and mandibles of an Australianbull ant. 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 vertebrates.
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 Forest scorpion (Cercophonius squama) is a scorpion native to southeastern Australia and Tasmania. The body is 25 to 40 millimetres (0.98 to 1.57 in) long, and coloured creamy yellow to orange brown with dark brown variegations. The legs are yellow with some dark brown pigment.
The light blue soldier crab (Mictyris longicarpus) inhabits beaches in the Indo-Pacific region. Soldier crabs filter sand or mud for microorganisms. They congregate during the low tide, and bury themselves in a corkscrew pattern during high tide, or whenever they are threatened.
A macro view of a Gonia capitatafly feeding on honey, showing its proboscis and 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 capillary action.
A female subimago of a March Brown mayfly (Rhithrogena germanica). Mayflies belong to the orderEphemeroptera, and the only insects that have a subimago phase. This stage is a favourite food of many fish, and many fishing flies are modeled to resemble them. They are aquatic insects whose nymph stage usually lasts one year in freshwater. The adults are short-lived, from as little as thirty minutes to a few days depending on the species.
Two flesh-flies (Sarcophaga ruficornis species pictured) mating. The life cycle of the saprophagic flesh-fly larvae has been well researched and is very predictable. Different species prefer bodies in different states of decomposition, which allows forensic entomologists to extrapolate the time of death.
Xylotrupes socrates (Siamese rhinoceros beetle, or "fighting beetle"), male, on a banana leaf. This scarab beetle is particularly known for its role in insect fighting in Northern Laos and Thailand.
Sympetrum danae, the black darter or black meadowhawk, is a species of dragonfly found in northern Europe, Asia, and North America. Both sexes are black and yellow, but the abdomen of the male is largely black while that of the female is largely yellow. Breeding takes place in shallow acidic pools, lake margins and ditches in lowland heaths and moorland bogs. The female lays her eggs during flight by dipping the tip of her abdomen into the water. The eggs hatch the following spring, the larvae developing very rapidly and emerging as adults in as little as two months. The male seen here is perched on a frond of bracken on Warren Heath in Hampshire, England.
Squilla mantis, a species of mantis shrimp, for sale at the fish auction of l'Ametlla de Mar in Catalonia, Spain. It is native to the Mediterranean Sea and adjacent warm parts of the Atlantic Ocean, where it burrows into muddy and sandy seabeds. It is the only native stomatopod to be fished for on a commercial scale in the Mediterranean.
Zonocerus variegatus, the variegated grasshopper, is a species of grasshopper in the family Pyrgomorphidae native to tropical western and central Africa. It feeds on a wide variety of plant foods and causes damage to crops, particularly cassava, groundnuts and vegetables, as well as transmitting diseases caused by mosaic viruses between plants. This Z. variegatus grasshopper was photographed in the Bobiri Forest in Ghana.
Danaus genutia, the common tiger or striped tiger, is a species of brush-footed butterfly found in Sri Lanka, India, Myanmar, south-eastern Asia and Australia. It prefers areas of moderate to heavy rainfall, and typical habitats include scrubby jungle, deciduous forests and fallow land near habitations. The insect sequesters toxins from plants, and advertises its unpalatability by having prominent markings and striking colour patterns. This adult male common tiger, of the subspecies D. g. genutia, was photographed in Kerala, India.
Poli's stellate barnacle (Chthamalus stellatus) is a species of acorn barnacle common on rocky shores in South West England, Ireland, and Southern Europe. It is named after Italian scientist Giuseppe Saverio Poli. Depending upon environmental conditions and the amount of food available, it can reach up to 14 mm (0.55 in) in diameter.
Attacus taprobanis is a species of moth in the family Saturniidae native to southern India and Sri Lanka. This adult male, photographed in Kadavoor, Kerala, developed from a larva feeding on a mahogany tree. When ready to pupate, the larva formed a papery cocoon 7.5 cm (3 in) long interwoven with a leaf; before doing this, the larva had attached the leaf to the stem with a silken thread and cut the leaf stalk. The colours of the dying leaf provided camouflage for the pupa, and the adult insect emerged some 24 days later.
The oriental hornet (Vespa orientalis) is a social insect in the family Vespidae, found in southern Europe, northeastern Africa, and western Asia. This worker, photographed in Sha'ar Poleg Reserve in Israel, is gathering nectar from a sea squill; adults will also feed on honeydew and fruit. They also capture insects such as grasshoppers, flies and honey bees to provide a diet high in protein for the colony's brood.
The cryptic mantis (Sibylla pretiosa) is a mantid native to southern Africa. Its common name comes from its ability to grow asymmetrically to match the vegetation of its environment. They have unusual leaf-like projections on the joint of their four walking legs and leaf-like wings, generally the only green portion of the insect's otherwise brown and mottled exoskeleton. Adult females grow to 5–6 cm (2.0–2.4 in) in length while the males are generally about 1 cm smaller.
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 Antarctica.
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