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...)
Out of the four described species of Slimonia, three measured below or up to 20 centimetres (7.9 in) in length. Only S. acuminata was larger, with the largest specimens measuring 100 centimetres (39 in) in length. Though this is large for a predatory arthropod, Slimonia would be exceeded in length by later and more derived (more "advanced") members of the closely related pterygotid family of eurypterids, which would become the largest known arthropods to ever live. (Full article...)
Haemolymph is the analogue of blood for most arthropods. An arthropod has an open circulatory system, with a body cavity called a haemocoel through which haemolymph circulates to the interior organs. 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 esophagus. The respiratory and 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-pitocelli 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, with many species giving birth to live young after the eggs have hatched inside the mother; but 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 social insects. (Full article...)
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Lycorma imperialis is a planthopperindigenous to parts of China and Indo-Malaysia. L. imperialis was originally discovered in 1846 by Adam White and has one recognized non-nominate subspecies, L. i. punicea. L. imperialis has undergone a number of reclassifications since its discovery and is one of four species in the genusLycorma. L. imperialis follows a hemimetabolous life cycle and will undergo a series of nymphal stages (instars) before maturing to an adult.
Lycorma imperialis and L. i. punicea are referred to as "lanternflies" or "lantern bugs" due to their crimson hindwings and their forewings, which can range from blue green to brick red. They do not, however, emit light. L. imperialis can cause substantial damage to agricultural industries due to its specialized, sap sucking mouthparts and the resulting mold that develops from its honeydew excrement. (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...)
Nanahughmilleria is classified in the family Adelophthalmidae, the only clade in the superfamily Adelophthalmoidea. This clade was characterised by their small size, their parabolic (approximately U-shaped) carapaces and the presence of epimera (lateral "extensions" of the segment) on the seventh segment, among others. Nanahughmilleria was different from its relatives by the presence of more spines in its appendages (limbs) and by its genital morphology. The largest species confidently assigned to the genus was N. norvegica at 10 cm (3.9 in), making it a comparatively small eurypterid. (Full article...)
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Fossil of J. rhenaniae, Natural History Museum, Mainz
Jaekelopterus is a genus of predatory eurypterid, a group of extinct aquatic arthropods. Fossils of Jaekelopterus have been discovered in deposits of Early Devonian age, from the Pragian and Emsian stages. There are two known species: the type species J. rhenaniae from brackish to fresh water strata in the Rhineland, and J. howelli from estuarine strata in Wyoming. The generic name combines the name of German paleontologist Otto Jaekel, who described the type species, and the Greek word πτερόν (pteron) meaning "wing".
Based on the isolated fossil remains of a large chelicera (claw) from the Klerf Formation of Germany, J. rhenaniae has been estimated to have reached a size of around 2.3–2.6 metres (7.5–8.5 ft), making it the largest arthropod ever discovered, surpassing other large arthropods such as fellow eurypterids Acutiramus and Pterygotus; the millipede Arthropleura. J. howelli was much smaller, reaching 80 centimetres (2.6 ft) in length.
In overall appearance, Jaekelopterus is similar to other pterygotid eurypterids, possessing a large, expanded telson (the hindmost segment of the body) and enlarged pincers and forelimbs. Both species of Jaekelopterus were first described as species of the closely related Pterygotus but were raised as a separate genus based on an observed difference in the genital appendage. Though this feature has since proved to be a misidentification, other features distinguishing the genus from its relatives have been identified, including a telson with a triangular shape and a different inclination of the denticles of the claws. (Full article...)
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Fossil of A. cummingsi
Acutiramus is a genus of giant predatory eurypterid, an extinct group of aquatic arthropods. Fossils of Acutiramus have been discovered in deposits of Late Silurian to Early Devonian age. Eight species have been described, five from North America (including A. cummingsi, the type species) and two from the Czech Republic (with one of them potentially found in Australia as well). The generic name derives from Latinacuto ("acute" or "sharp") and Latin ramus ("branch"), referring to the acute angle of the final tooth of the claws relative to the rest of the claw.
Acutiramus is classified as part of the eurypterid family Pterygotidae, a family differentiated from other eurypterids by their flattened telsons (the most posterior segment of the body) and their modified chelicerae (frontal appendages), ending in well-developed chelae (claws). Many pterygotid eurypterids, such as Jaekelopterus and Pterygotus, grew to gigantic proportions. Acutiramus was no exception, with the largest species, A. bohemicus, surpassing 2 metres (6.6 feet) in length. All species were not this large though, with some (such as A. floweri) only reaching lengths of 20 centimetres (7.9 in).
Other giant pterygotid eurypterids, such as Jaekelopterus and Pterygotus, were very visually acute (possessed good and sharp eyesight) in a similar way to modern predatory arthropods and possessed robust and crushing chelae. Studies on the compound eyes and chelicerae of Acutiramus has revealed that it would have had a comparably low visual acuity and claws adapted for slicing and shearing, rather than crushing. This suggests that the ecological role of Acutiramus was distinct from that of other pterygotids, it potentially lived a lifestyle of ambush predation or scavenging on soft-bodied animals, feeding during the night or in otherwise low-light conditions. (Full article...)
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Plexippoides regius in South Korea
Plexippoides regius (Korean: 왕어리두줄깡충거미; RR: Wangeoridujulkkangchunggeomi) is a species of jumping spider in the genusPlexippoides. The species was first described by Wanda Wesołowska in 1981 based on specimens from North Korea but its distribution has been extended to include China, Russia and South Korea, with examples found as far as Sichuan. The spider is small, with a body length between 6.9 and 8.65 mm (0.27 and 0.34 in), the female being generally larger than the male. It is distinguished by the two brown lines that stretch across the back of its carapace and abdomen that is recalled in its Korean name. Otherwise, the spider varies in coloration, with some examples having an orange or yellow-brown carapace and others dark brown. The male has a long embolus that encircles the palpal bulb. The female has complex seminal ducts that lead to heavily sclerotised and many-chambered spermathecae. (Full article...)
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Kleptoparasitism (originally spelt clepto-parasitism, meaning "parasitism by theft") is a form of feeding in which one animal deliberately takes food from another. The strategy is evolutionarily stable when stealing is less costly than direct feeding, such as when food is scarce or when victims are abundant. Many kleptoparasites are arthropods, especially bees and wasps, but including some true flies, dung beetles, bugs, and spiders. Cuckoo bees are specialized kleptoparasites which lay their eggs either on the pollen masses made by other bees, or on the insect hosts of parasitoid wasps. They are an instance of Emery's rule, which states that insect social parasites tend to be closely related to their hosts. The behavior occurs, too, in vertebrates including birds such as skuas, which persistently chase other seabirds until they disgorge their food, and carnivorous mammals such as spotted hyenas and lions. Other species opportunistically indulge in kleptoparasitism. (Full article...)
Eucteniza (/juːktəˈnaɪzə/yook-tə-NY-zə) is a genus of trapdoor spiders in the family Euctenizidae containing at least 14 species occurring in Mexico and the southern United States. Species are distinguished by a softened rear portion of the carapace, and males possess large spines on the first two pairs of walking legs that are used to hold females during mating. Like other trapdoor spiders they create burrows with a hinged lid, from which they await passing insects and other arthropods to prey upon. Many species are known from only one or two localities, or from only male specimens. More species are expected to be discovered. Eucteniza is closely related to spiders of the genera Entychides and Neoapachella. (Full article...)
Restoration of the pretelson and telson of H. suecicus, showing the cercal blades, following Kjellesvig-Waering (1979)
Holmipterus is a problematic genus of eurypterid, an extinct group of aquatic arthropods. The type and only species of Holmipterus, H. suecicus, is known from deposits of Middle Silurian age in the Sweden. The generic name honours Gerhard Holm [sv], a renowned Swedish palaeontologist specialising in arthropods and crustaceans, and the species name suecicus is Latin for 'Swedish'.
Although Holmipterus was a large eurypterid and is known from multiple, albeit partial and fragmentary, specimens, it has proven difficult to determine where it fits in the eurypterid family tree. This is due to the fossil material referred to Holmipterus combining traits seen in different eurypterid groups, such as the Carcinosomatidae and Megalograptidae, and has some distinctive features, such as a telson (the posteriormost division of the body) with two articulating 'cercal blades', forming an organ capable of grasping. Though often classified either as a carcinosomatid or megalograptid, Holmipterus has also been classified as a genus of uncertain affinity within the Eurypterina suborder, or within the entire Eurypterida order. It is possible that the original 1979 description of Holmipterus suecicus reconstructed the telson inaccurately, and/or mistakenly combined fossil material actually belonging to two different genera. (Full article...)
Mysida is an order of small, shrimp-like crustaceans in the malacostracansuperorderPeracarida. Their common nameopossum shrimps stems from the presence of a brood pouch or "marsupium" in females. The fact that the larvae are reared in this pouch and are not free-swimming characterises the order. The mysid's head bears a pair of stalked eyes and two pairs of antennae. The thorax consists of eight segments each bearing branching limbs, the whole concealed beneath a protective carapace and the abdomen has six segments and usually further small limbs.
Theridion grallator, also known as the Hawaiian happy-face spider, is a spider in the familyTheridiidae that resides on the Hawaiian Islands. T. grallator gets its vernacular name of "Hawaiian happy-face spider" from the unique patterns superimposed on its abdomen, specifically those that resemble a human smiling face. T. grallator is particularly notable because of its wide range of polymorphisms that may be studied to allow a better understanding of evolutionary mechanisms. In addition to the variety of color polymorphisms present, T. grallator demonstrates the interesting quality of diet-induced color change, in which its appearance temporarily changes as it metabolizes various food items. (Full article...)
Prionomyrmecini is an anttribe belonging to the subfamily Myrmeciinae established by William Morton Wheeler in 1915. Two members are a part of this tribe, the extant Nothomyrmecia and the extinct Prionomyrmex. The tribe was once considered a subfamily due to the similarities between Nothomyrmecia and Prionomyrmex, but such reclassification was not widely accepted by the scientific community. These ants can be identified by their long slender bodies, powerful stingers and elongated mandibles. Fossil Prionomyrmecini ants were once found throughout Europe, possibly nesting in trees and preferring jungle habitats. Today, Prionomyrmecini is only found in Australia, preferring old-growth mallee woodland surrounded by Eucalyptus trees. Nothomyrmecia workers feed on nectar and arthropods, using their compound eyes for prey and navigational purposes. Owing to their primitive nature, they do not recruit others to food sources or create pheromone trails. Nothomyrmecia colonies are small, consisting of 50 to 100 individuals. (Full article...)
Image 5Some 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 6The fangs in spiders' chelicerae are so sclerotised as to be greatly hardened and darkened (from Arthropod exoskeleton)
Image 7Body structure of a typical crustacean – krill (from Crustacean)
Image 8In 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)
Image 9Decapods, from Ernst Haeckel's 1904 work Kunstformen der Natur (from Crustacean)
Image 10This 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 12Formation 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 14Ghost 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 16 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 23The 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 30Mature 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)
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 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 honey bee extracts nectar from a flower using its proboscis. Tiny hairs covering the bee's body maintain a slight electrostatic charge, causing pollen from the flower's anthers to stick to the bee's hairs, allowing for pollination when the bee moves on to another flower.
Argiope trifasciata, the banded garden or banded orb-weaving spider, is a species of arachnid in the family Araneidae. It is native to North and South America but has spread to other parts of the world. This ventral view of a female A. trifasciata shows her in the centre of her web, which can reach a diameter of 60 cm (24 in). The function of the zig-zag web decorations is unclear, but they may serve to make the spider appear larger or to act as a warning sign.
Two Melangyna viridiceps (called Common Hoverflies in Australia) mating in mid-air. The male, which can be identified by the eyes meeting at the top of its head, is on top. The term "hoverfly" refers to about 6,000 species of flying insects in the family Syrphidae. They are often seen hovering at flowers and are important pollinators.
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.
The Polyphemus Moth (Anthera polyphemus) is one the biggest moths, having a wingspan of up to 15 cm. Usually found in forests, moths are notable for apparently being attracted to light, the reason for this behaviour is not known.
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.
The red rock crab (Grapsus grapsus) is one of the most common crabs along the western coast of the Americas. Adults are quite variable in color, including brownish-red, mottled or spotted brown, pink, yellow, bright orange and red. It feeds on algae primarily, sometimes sampling other plant matter and dead animals.
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.
The red rock crab (Grapsus grapsus), also known as "Sally Lightfoot", is one of the commonest crabs along the western seaboard of the Americas. John Steinbeck wrote of them, "Everyone who has seen them has been delighted with them ... These little crabs, with brilliant cloisonné carapaces, walk on their tiptoes, they have remarkable eyes and an extremely fast reaction time." He tried to catch them but to little avail. "If you walk slowly, they move slowly ahead of you in droves. If you hurry, they hurry. When you plunge at them, they seem to disappear in a puff of blue smoke."
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.
Purana tigrina is a species of cicada found in Southeast Asia. This adult male was photographed in Kadavoor, Kerala, in southern India, and is about one inch (25 mm) in length. The mouthparts are adapted to piercing plant tissues and sucking sap; the male abdomen houses the tymbal, an organ used in the production of song, while the female abdomen is tipped by a large, saw-edged ovipositor.
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.
Two Eastern Lubber grasshoppers (Romalea guttata) mating. Native to the southeastern and south central portion of the United States, it is well known both for its size and its unique coloration. During reproduction, the male grasshopper introduces sperm into the ovipositor through its aedeagus (reproductive organ), and inserts its spermatophore, a package containing the sperm, into the female's ovipositor.
The monarch butterfly (Danaus plexippus) is one of the best-known species of butterfly. Its wings feature an easily recognizable orange and black pattern, with a wingspan of 8.9–10.2 centimetres (3½–4 in).
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 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.
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