Urticating hairs or urticating bristles, i.e. irritating hairs, are one of the primary defense mechanisms used by numerous plants all New World tarantulas, various lepidopteran caterpillars. Urtica is Latin for "nettle", hairs that urticate are characteristic of this type of plant, many other plants in several families; this term refers to certain types of barbed hairs that cover the dorsal and posterior surface of a tarantula's or caterpillar's abdomen. Many tarantula species eject hairs from their abdomens; these hairs can embed themselves in the other animal's skin or eyes, causing physical irritation to great discomfort. The most common form of urticating hairs in plants are typified by nettles, which possess sharp-pointed hollow hairs seated on a gland that secretes an acrid fluid; the points of these hairs break off in the wound, the acrid fluid is pressed into it. Various plants unrelated to true nettles possess similar defensive hairs, the common names reflect this. Several lepidopteran families include.
Families prominent in this respect include the following: Adults of some species have urticating scales, some species shed some of their urticating hairs as defense for their pupae and eggs. The urticating setae or spines can lodge in skin. In some species these structures are hollow and connected to venom-producing cells, functioning like a hypodermic needle. Most hairs are only irritating, but some are dangerous to the eyes and respiratory tract, some can cause severe skin necrosis and shedding. Certain species of Lonomia in the family Saturniidae can inject venom, life-threatening to humans; the stings are not part of a deliberate attack, but are the result of brushing against the spines. However, many species whose larvae are armed with such hairs have behavioral patterns adapted to present the urticating hairs as a defensive threat and to inflict them on any perceived attackers. For example, many larvae in the family Lasiocampidae bear dense bands of short stinging hairs across their thoracic segments.
The hairs are retracted into a shallow fold in the skin, but if the caterpillar is disturbed, it everts the folds and displays the hairs, which are of a contrasting color. If stimulated or gripped, lasiocampid larvae are to lash about, forcing the stinging hairs into any vulnerable organ within reach. Many other species of larvae lack any such localized concentrations of hairs and are armed more with urticating hairs. Toxins from the broken hairs may spill out. For brown-tail moths native to Europe and invasive in other parts of the world, hairs are shed or broken off during molts and can be wind-borne, so that direct contact with live or dead larvae is not required to trigger a rash. In spite of such defenses, some species of birds feed avidly on hairy caterpillars, they grab them in their beaks and scrub them on the ground till the majority of the hairs have been stripped or damaged, but at least some species of cuckoos collect the hairs in the digestive tract until they form pellets that can be regurgitated.
Examples of avian predators other than cuckoos that feed on hairy caterpillars include at least tens of species from several continents. Urticating hairs are found in about 90% of the species of tarantula found in the New World, they are not found in tarantulas from other parts of the world. Urticating hairs do not appear at birth but form with each consecutive molt, widening from molt to molt and outwardly presenting themselves around areas of more dark hairs on the upper back part of the abdomen of juveniles. In elder ages their coloration shifts to match the main tone of abdomen. Despite this shift, urticating hairs nonetheless retain unique characteristics that render them visually distinct from abdominal hairs, such as their tendency to cover only a portion instead of the entirety of the opisthosoma. There are six different types of urticating hair known in tarantulas, varying in size and shape the distribution of barbs. Type I Type II Type III Type IV Type V Type VIEach type of urticating hair is believed to target different enemies.
Defined targets for some hair types are unknown. Type II is not kicked off by the tarantula, rather delivered by direct contact. However, there is at least one aviculariine species - Caribena versicolor - which can kick type II urticating hairs off of the abdomen to species from the subfamily Theraphosinae. Tarantulas from the genera Avicularia and Iridopelma possess Type II hairs. Type III urticating hairs are most efficient for defense against invertebrates. Types III and IV are the most irritating to mammalian predators. Not all urticating hair types are exhibited by each species of tarantula. Type II urticating hairs can be found in the genera Avicularia and Pachistopelma. Type I and III urticating hairs are representative on a wide diversity of large bodied genera in the subfamily Theraphosinae Lasiodora and Acanthoscurria Nhandu spp. Megaphobema spp. Sericopelma spp. Eupalaestrus spp. Proshapalopus spp. Brachypelma spp. Cyrtopholis spp. and others, although some only have Type I in mature males.
Unusually, Type III urticating hair is found alone on the
Spider behavior refers to the range of behaviors and activities performed by spiders. Spiders are air-breathing arthropods that have eight legs and chelicerae with fangs that inject venom, they are the largest order of arachnids and rank seventh in total species diversity among all other groups of organisms, reflected in their large diversity of behavior. All known spider species are predators preying on insects and on other spiders, although a few species take vertebrates such as frogs, lizards and birds and bats. Spiders' guts are too narrow to take solids, they liquidize their food by flooding it with digestive enzymes and grinding it with the bases of their pedipalps, as they do not have true jaws. Though most known spiders are exclusively carnivorous, a few species of jumping spiders, supplement their diet with plant matter such as sap and pollen. However, most of these spiders still need a carnivorous diet to survive, lab studies have shown that they become unhealthy when fed only plants.
One exception is a species of jumping spider called Bagheera kiplingi, herbivorous, feeding on the sugar rich Beltian bodies produced by acacia plants. Many spiders, but not all, build webs. Other spiders use a wide variety of methods to capture prey. Web: There are several recognised types of spider web Spiral orb webs, associated with the family Araneidae Tangle webs or cobwebs, associated with the family Theridiidae Funnel webs, Tubular webs, which run up the bases of trees or along the ground Sheet websThe net-casting spider weaves a small net which it attaches to its front legs, it lurks in wait for potential prey and when such prey arrives, lunges forward to wrap its victim in the net and paralyze it. Hence, this spider expends less energy catching prey than a primitive hunter and avoids the energy loss of weaving a large orb web. Bolas: Bolas spiders are unusual orb-weaver spiders that do not spin the webs. Instead, they hunt by using a sticky'capture blob' of silk on the end of a line, known as a'bolas'.
By swinging the bolas at flying male moths or moth flies nearby, the spider may snag its prey rather like a fisherman snagging a fish on a hook. Because of this, they are called angling or fishing spider; the prey is lured to the spider by the production of up to three pheromone analogues. Hunting on land: Jumping spiders, Wolf spiders and many other types of spiders hunt freely; some of these have enhanced sometimes approaching that of a pigeon. They are robust and agile; some are opportunistic hunters pouncing upon prey as they find it or chasing it over short distances. Some will wait for passing prey near the mouth of a burrow. Hunting on water: Dolomedes spiders hunt by waiting at the edge of a pool or stream, they hold on to the shore with their back legs while the rest of their body lies on the water, with legs stretched out. When they detect the ripples from prey, they run across the surface to subdue it using their foremost legs, which are tipped with small claws, they eat insects, but some larger species are able to catch small fish.
Females of the water spider Argyroneta aquatica build underwater "diving bell" webs which they fill with air and use for digesting prey, molting and raising offspring. They live entirely within the bells, darting out to catch prey animals that touch the bell or the threads that anchor it. Deception: Some spiders hunt other spiders using deception; this attracts the owner of the web whereupon Portia overwhelms the owner. Trapdoor: Trapdoor spiders construct burrows with a cork-like trapdoor made of soil and silk; the trapdoor is difficult to see when it is closed because the plant and soil materials camouflage it. The trapdoor is hinged on one side with silk; the spiders wait for prey while holding on to the underside of the door. Prey is captured when insects, other arthropods, or small vertebrates disturb the'trip' lines the spider lays out around its trapdoor, alerting the spider to a meal within reach; the spider detects the prey by vibrations and, when it comes close enough, leaps out of its burrow to make the capture.
Some Conothele species do not build a burrow, but construct a silken tube with trapdoor in bark crevices. Basket: The Kaira spider uses a pheromone to attract moths and catches the insects with a basket formed from its legs. Spiders perform cannibalism under a range of circumstances. Females eating males: Perhaps the most known example of cannibalism in spiders is when females cannibalise males before, during or after copulation. For example, the male Australian redback spider is killed by the female after he inserts his second palpus in the female's genital opening. However, the theory of the "sacrificial male" may have become greater than the truth; some believe. Males eating females: Male water spiders, show a predilection for mating with larger females, while cannibalizing females smaller than themselves. Sacrificial mothers: Offspring of the species Stegodyphus lineatus eat their mother. Females of Segestria florentina sometimes die while guarding her eggs and the hatched spiders eat her. Non-reproductive cannibalism: Some spiders, such as Pholcus phalangioides, will prey on their own kind when food is scarce.
Death feigning can be used in reproductive behavior of spiders. In
The arthropod leg is a form of jointed appendage of arthropods used for walking. Many of the terms used for arthropod leg segments are of Latin origin, may be confused with terms for bones: coxa, femur, tarsus, metatarsus, dactylus, patella. Homologies of leg segments between groups are difficult to prove and are the source of much argument; some authors posit up to eleven segments per leg for the most recent common ancestor of extant arthropods but modern arthropods have eight or fewer. It has been argued that the ancestral leg need not have been so complex, that other events, such as successive loss of function of a Hox-gene, could result in parallel gains of leg segments; the appendages of arthropods may be either uniramous. A uniramous limb comprises a single series of segments attached end-to-end. A biramous limb, branches into two, each branch consists of a series of segments attached end-to-end; the external branch of the appendages of crustaceans is known as the exopod or exopodite, while the internal branch is known as the endopod or endopodite.
Other structures aside from the latter two are termed endites. Exopodites can be distinguished from exites by the possession of internal musculature; the exopodites can sometimes be missing in some crustacean groups, they are absent in insects. The legs of insects and myriapods are uniramous. In crustaceans, the first antennae are uniramous, but the second antennae are biramous, as are the legs in most species. For a time, possession of uniramous limbs was believed to be a shared, derived character, so uniramous arthropods were grouped into a taxon called Uniramia, it is now believed that several groups of arthropods evolved uniramous limbs independently from ancestors with biramous limbs, so this taxon is no longer used. Arachnid legs differ from those of insects by the addition of two segments on either side of the tibia, the patella between the femur and the tibia, the metatarsus between the tibia and the tarsus, making a total of seven segments; the situation is identical with the addition of a pre-tarsus beyond the tarsus.
The claws of the scorpion are not legs, but are pedipalps, a different kind of appendage, found in spiders and is specialised for predation and mating. In Limulus, there are no pretarsi, leaving six segments per leg; the legs of crustaceans are divided primitively into seven segments, which do not follow the naming system used in the other groups. They are: coxa, ischium, carpus and dactylus. In some groups, some of the limb segments may be fused together; the claw of a lobster or crab is formed by the articulation of the dactylus against an outgrowth of the propodus. Crustacean limbs differ in being biramous, whereas all other extant arthropods have uniramous limbs. Myriapods have seven-segmented walking legs, comprising coxa, prefemur, tibia, a tarsal claw. Myriapod legs show a variety of modifications in different groups. In all centipedes, the first pair of legs is modified into a pair of venomous fangs called forcipules. In most millipedes, one or two pairs of walking legs in adult males are modified into sperm-transferring structures called gonopods.
In some millipedes, the first leg pair in males may be reduced to tiny hooks or stubs, while in others the first pair may be enlarged. Insects and their relatives are hexapods, having six legs, connected to the thorax, each with five components. In order from the body they are the coxa, femur and tarsus; each is a single segment, except the tarsus which can be from three to seven segments, each referred to as a tarsomere. A representative insect leg, such as that of a housefly or cockroach, has the following parts, in sequence from most proximal to most distal: coxa trochanter femur tibia tarsus pretarsus. Associated with the leg itself there are various sclerites around its base, their functions are articular and have to do with how the leg attaches to the main exoskeleton of the insect. Such sclerites differ between unrelated insects; the coxa is the proximal functional base of the leg. It articulates with the pleuron and associated sclerites of its thoracic segment, in some species it articulates with the edge of the sternite as well.
The homologies of the various basal sclerites are open to debate. Some authorities suggest. In many species the coxa has two lobes; the posterior lobe is the meron, the larger part of the coxa. A meron is well developed in Periplaneta, the Isoptera and Lepidoptera; the trochanter articulates with the coxa but is attached rigidly to the femur. In some insects its appearance may be confusing. In parasitic Hymenoptera the base of the femur has the appearance of a second trochanter. In most insects the femur is the largest region of the leg; the tibia is the fourth section of the typical insect leg. As a rule the tibia of an insect is slender in comparison to the femur, but it is at least as long and longer. Near the dis
Ecdysis is the moulting of the cuticle in many invertebrates of the clade Ecdysozoa. Since the cuticle of these animals forms a inelastic exoskeleton, it is shed during growth and a new, larger covering is formed; the remnants of the old, empty exoskeleton are called exuviae. After moulting, an arthropod is described as a callow. Within one or two hours, the cuticle hardens and darkens following a tanning process analogous to the production of leather. During this short phase the animal expands, since growth is otherwise constrained by the rigidity of the exoskeleton. Growth of the limbs and other parts covered by hard exoskeleton is achieved by transfer of body fluids from soft parts before the new skin hardens. A spider with a small abdomen may be undernourished but more has undergone ecdysis; some arthropods large insects with tracheal respiration, expand their new exoskeleton by swallowing or otherwise taking in air. The maturation of the structure and colouration of the new exoskeleton might take days or weeks in a long-lived insect.
Ecdysis allows damaged tissue and missing limbs to be regenerated or re-formed. Complete regeneration may require a series of moults, the stump becoming a little larger with each moult until it is a normal, or near normal, size; the term ecdysis comes from Ancient Greek: ἐκδύω, "to take off, strip off". In preparation for ecdysis, the arthropod becomes inactive for a period of time, undergoing apolysis or separation of the old exoskeleton from the underlying epidermal cells. For most organisms, the resting period is a stage of preparation during which the secretion of fluid from the moulting glands of the epidermal layer and the loosening of the underpart of the cuticle occur. Once the old cuticle has separated from the epidermis, a digesting fluid is secreted into the space between them. However, this fluid remains inactive. By crawling movements, the organism pushes forward in the old integumentary shell, which splits down the back allowing the animal to emerge; this initial crack is caused by a combination of movement and increase in blood pressure within the body, forcing an expansion across its exoskeleton, leading to an eventual crack that allows for certain organisms such as spiders to extricate themselves.
While the old cuticle is being digested, the new layer is secreted. All cuticular structures are shed at ecdysis, including the inner parts of the exoskeleton, which includes terminal linings of the alimentary tract and of the tracheae if they are present; each stage of development between moults for insects in the taxon endopterygota is called an instar, or stadium, each stage between moults of insects in the Exopterygota is called a nymph: there may be up to 15 nymphal stages. Endopterygota tend to have only five instars. Endopterygotes have more alternatives to moulting, such as expansion of the cuticle and collapse of air sacs to allow growth of internal organs; the process of moulting in insects begins with the separation of the cuticle from the underlying epidermal cells and ends with the shedding of the old cuticle. In many species it is initiated by an increase in the hormone ecdysone; this hormone causes: apolysis – the separation of the cuticle from the epidermis secretion of new cuticle materials beneath the old degradation of the old cuticleAfter apolysis the insect is known as a pharate.
Moulting fluid is secreted into the exuvial space between the old cuticle and the epidermis, this contains inactive enzymes which are activated only after the new epicuticle is secreted. This prevents the new procuticle from getting digested; the lower regions of the old cuticle, the endocuticle and mesocuticle, are digested by the enzymes and subsequently absorbed. The exocuticle and epicuticle are hence shed at ecdysis. Spiders change their skin for the first time while still inside the egg sac, the spiderling that emerges broadly resembles the adult; the number of moults varies, both between species and genders, but will be between five times and nine times before the spider reaches maturity. Not since males are smaller than females, the males of many species mature faster and do not undergo ecdysis as many times as the females before maturing. Members of the Mygalomorphae are long-lived, sometimes 20 years or more. Spiders stop feeding at some time before moulting for several days; the physiological processes of releasing the old exoskeleton from the tissues beneath cause various colour changes, such as darkening.
If the old exoskeleton is not too thick it may be possible to see new structures, such as setae, from outside. However, contact between the nerves and the old exoskeleton is maintained until a late stage in the process; the new, teneral exoskeleton has to accommodate a larger frame than the previous instar, while the spider has had to fit into the previous exoskeleton until it has been shed. This means the spider does not fill out the new exoskeleton so it appears somewhat wrinkled. Most species of spiders hang from silk during the entire process, either dangling from a drop line, or fastening their claws into webbed fibres attached to a suitable base; the discarded, dried exoskeleton remains hanging where it was abandoned once the spider has left. To open the old exoskeleton, the spider contracts its abdomen to supply enough fluid to pump into the prosoma with sufficient pressure to crack it open alo
Anyphops is a genus of African wall spiders first described by P. L. Benoit in 1968; as of 2017, it contains 64 African species: Anyphops alticola Anyphops amatolae Anyphops atomarius Anyphops barbertonensis Anyphops barnardi Anyphops basutus Anyphops bechuanicus Anyphops benoiti Corronca, 1998 Anyphops braunsi Anyphops broomi Anyphops caledonicus Anyphops capensis Anyphops civicus Anyphops decoratus Anyphops dubiosus Anyphops dulacen Corronca, 2000 Anyphops fitzsimonsi Anyphops gilli Anyphops helenae Anyphops hessei Anyphops hewitti Anyphops immaculatus Anyphops karrooicus Anyphops kivuensis Benoit, 1968 Anyphops kraussi Anyphops lawrencei Anyphops leleupi Benoit, 1972 Anyphops lesserti Anyphops lignicola Anyphops lochiel Corronca, 2000 Anyphops longipedatus Anyphops lucia Corronca, 2005 Anyphops lycosiformis Anyphops maculosus Anyphops marshalli Anyphops minor Anyphops montanus Anyphops mumai Anyphops namaquensis Anyphops narcissi Benoit, 1972 Anyphops natalensis Anyphops ngome Corronca, 2005 Anyphops parvulus Anyphops phallus Anyphops pococki Anyphops purcelli Anyphops regalis Anyphops reservatus Anyphops rubicundus Anyphops schoenlandi Anyphops septemspinatus Anyphops septentrionalis Benoit, 1975 Anyphops sexspinatus Anyphops silvicolellus Anyphops smithersi Anyphops spenceri Anyphops sponsae Anyphops stauntoni Anyphops stridulans Anyphops thornei Anyphops transvaalicus Anyphops tuckeri Anyphops tugelanus Anyphops whiteae
The epigyne or epigynum is the external genital structure of female spiders. As the epigyne varies in form in different species in related ones, it provides the most distinctive characteristic for recognizing species, it consists of a small, hardened portion of the exoskeleton located on the underside of the abdomen, in front of the epigastric furrow and between the epigastric plates. The primary function of the epigyne is to receive and direct the palpal organ of the male during copulation; the various specific forms of epigynes are correlated, in each case, with corresponding specific differences in the palpus of the male. This specialization prevents individuals of different species from mating; the epigyne covers or accompanies the openings of the spermathecae, which are pouches for receiving and retaining sperm. The openings of the spermathecae are on the outer face of the epigyne and can be seen. A secondary function of the epigyne is as an ovipositor. An example of a comparatively simple epigyne is that of Pirata montanus.
It consists of a nearly plain plate, with the openings of the spermathacae near the posterior lateral corners. A somewhat more complicated form is illustrated by the epigyne of Trabeops aurantiacus. In this species, the plate is depressed or furrowed longitudinally, the depressed area is divided by a ridge-like elevation, which divides the depression into two furrows or channels, each of which leads to the opening of the spermatheca of the corresponding side; this ridge-like elevation is called the guide, as its function "seems to be that of a guide to the male embolus, controlling the course of the latter and facilitating its entrance to the spermatheca." In many cases the guide extends laterally on each side at its posterior end. This is true to a slight extent in the epigyne of Trabeops, but more markedly so in that of many species of Geolycosa, where the lateral expansions conceal the openings of the spermathecae, as in the epigyne of Geolycosa pikei. A more complicated form of epigyne is found in spiders of the genus Araneus, where there is developed an appendage, soft and flexible, and, termed the scape or ovipositor.
When there is a well-developed scape, the tip of it is more or less spoon-shaped. This part of the scape is termed the cochlear; the basal plate of the epigyne which bears the scape, which forms a porch or hood that covers the opening of the oviduct is called the atriolum. A still more complicated form of epigyne is found in some of the sheet weavers and orb weavers, where the ovipositor consists of two finger-like projections: first, the more common one, the scape, which arises from the atriolum, in front of the opening of the oviduct; each of these projections may be grooved on the side facing the oviduct. This article incorporates text from a publication now in the public domain: The Spider Book
Evolution of spiders
The evolution of spiders has been going on for at least 380 million years, since the first true spiders evolved from crab-like chelicerate ancestors. More than 45,000 extant species have been described, organised taxonomically in 3,958 genera and 114 families. There may be more than 120,000 species. Fossil diversity rates make up a larger proportion than extant diversity would suggest with 1,593 arachnid species described out of 1,952 recognized chelicerates. Both extant and fossil species are described yearly by researchers in the field. Major developments in spider evolution include the development of spinnerets and silk secretion. Among the oldest known land arthropods are Trigonotarbids, members of an extinct order of spider-like arachnids. Trigonotarbids share many superficial characteristics with spiders, including a terrestrial lifestyle, respiration through book lungs, walking on eight legs, with a pair of leg-like pedipalps near the mouth and mouth parts. Arguments still remain open as to.
This had been a popular thought for quite some time, until an unpublished fossil was described with distinct microtubercles on its hind legs, akin to those used by spiders to direct and manipulate their silk. Trigonotarbids are not true spiders, most Trigonotarbid species have no living descendants today. One lineage, led to the earliest tetrapulmonates, which evolved into spiders, whip scorpions, close relatives. At one stage the oldest fossil spider was believed to be Attercopus which lived 380 million years ago during the Devonian. Attercopus was placed as the sister-taxon to all living spiders, but has now been reinterpreted as a member of a separate, extinct order Uraraneida which could produce silk, but did not have true spinnerets; the oldest true spiders date to about 300 million years ago. Most of these early segmented fossil spiders from the Coal Measures of Europe and North America belonged to the Mesothelae, or something similar, a group of primitive spiders with the spinnerets placed underneath the middle of the abdomen, rather than at the end as in modern spiders.
They were ground-dwelling predators, living in the giant clubmoss and fern forests of the mid-late Palaeozoic, where they were predators of other primitive arthropods. Silk may have been used as a protective covering for the eggs, a lining for a retreat hole, perhaps for simple ground sheet web and trapdoor construction; as plant and insect life diversified so did the spider's use of silk. Spiders with spinnerets at the end of the abdomen appeared more than 250 million years ago promoting the development of more elaborate sheet and maze webs for prey capture both on ground and foliage, as well as the development of the safety dragline; the oldest mygalomorph, was described from the Triassic of France and belongs to the modern family Hexathelidae. Megarachne servinei from the Permo-Carboniferous was once thought to be a giant mygalomorph spider and, with its body length of 1 foot and leg span of above 20 inches, the largest known spider to have lived on Earth, but subsequent examination by an expert revealed that it was a small sea scorpion.
By the Jurassic, the sophisticated aerial webs of the orb-weaver spiders had developed to take advantage of the diversifying groups of insects. A spider web preserved in amber, thought to be 110 million years old, shows evidence of a perfect "orb" web, the most famous, circular kind one thinks of when imagining spider webs. An examination of the drift of those genes thought to be used to produce the web-spinning behavior suggests that orb spinning was in an advanced state as many as 136 million years ago. One of these, the araneid Mongolarachne jurassica, from about 165 million years ago, recorded from Daohuogo, Inner Mongolia in China, is the largest known fossil spider; the 110-million-year-old amber-preserved web is the oldest to show trapped insects, containing a beetle, a mite, a wasp's leg, a fly. The ability to weave orb webs is thought to have been "lost", sometimes re-evolved or evolved separately, in different breeds of spiders since its first appearance. Spider taxonomy Insect evolution Brunetta, Leslie.
Spider silk: evolution and 400 million years of spinning, waiting and mating. New Haven: Yale University Press. ISBN 978-0-300-14922-7. Penney, D.. Dominican Amber Spiders: a comparative neontological approach to identification faunistics ecology and biogeography. Manchester: Siri Scientific Press. ISBN 978-0-9558636-0-8. Penney, D.. A.. Fossil Spiders: the evolutionary history of a mega-diverse order. Manchester: Siri Scientific Press. ISBN 978-0-9558636-5-3. Picture of spider fossil Dunlop, J. A. Penney, D. & Jekel, D.. A summary list of fossil spiders and their relatives. World Spider Catalog. Natural History Museum Bern, online at http://wsc.nmbe.ch, version 16.5