1.Brazilian wandering spiders or banana spiders
Phoneutria, commonly known as Brazilian wandering spiders or banana spiders, are a genus of defensive and highly venomous spiders found in tropical South and Central America. These spiders are members of the Ctenidae family of wandering spiders.
The Brazilian wandering spiders appear in Guinness World Records from 2010 to present as the world’s most venomous spider.
The Brazilian wandering spiders can grow to have a leg span of up to 13–15 cm (4–5 in). Their body length ranges from 17 to 48 mm (0.7–1.9 in).Wandering spiders are so-called because they wander the jungle floor at night, rather than residing in a lair or
Brazilian Wandering Spider
maintaining a web. During the day they hide inside termite mounds, under fallen logs and rocks, and in banana plants and bromeliads. P. nigriventer is known to hide in dark and moist places in or near human dwellings.
P. nigriventer mates during the dry season from April to June, which leads to frequent observations of the species during this time.
They have a distinctive defensive display in which the body is lifted up into an erect position, the first two pairs of legs are lifted high (revealing the conspicuous black-striped pattern on their underside), while the spider sways from side to side with hind legs in a cocked position.
Phoneutria fera andPhoneutrianigriventer are widely considered the most venomous species of spider. Its venom contains a potent neurotoxin, known as PhTx3, which acts as a broad-spectrum calcium channel blocker that inhibits glutamate release, calcium uptake and also glutamate uptake in neural synapses. At deadly concentrations, this neurotoxin causes loss of muscle control and breathing problems, resulting in paralysis and eventual asphyxiation. In addition, the venom causes intense pain and inflammation following a bite due to an excitatory effect the venom has on the serotonin 5-HT4 receptors of sensory nerves. This sensory nerve stimulation causes a release of neuropeptides such as substance P which triggers inflammation and pain.
Aside from causing intense pain, the venom of the spider can also cause priapism in humans. Erections resulting from the bite are uncomfortable, can last for many hours and can lead to impotence. A component of the venom (Tx2-6) is being studied for use in erectile dysfunction treatments.
The spider’s wandering nature is another reason it is considered so dangerous. In densely populated areas, Phoneutria species usually search for cover and dark places to hide during daytime, leading it to hide within houses, clothes, cars, boots, boxes and log piles, thus generating accidents when people disturb it. Its other common name, “banana spider”, comes from its tendency to hide in banana bunches or plantations, and it is occasionally found as a stowaway within shipments of bananas. These spiders can also appear in banana crates sent to grocery stores and bulk food centers around the world. One such instance happened in 2005 with a shipment of bananas arriving at Bridgwater, England, when a man was bitten by a P. fera; however, due to quick medical care he survived, taking nearly a week to recover from the bite following treatment.
The venom from the Brazilian wandering spider is so toxic that 0.006 mg of it can kill a mouse.
2.Australian funnel-web spider
Atracinae, commonly known as Australian funnel-web spiders, is a subfamily of spiders in the funnel-web spider family Hexathelidae.These spiders are medium-to-large in size, with body lengths ranging from 1 cm to 5 cm (0.4″ to 2″). They are darkly coloured, ranging from black to blue-black to plum to brown, with a glossy, hairless carapace covering the front part of the body. Like the related diplurid spiders, some hexathelids have relatively long spinnerets; this is especially true of A. robustus.
Funnel-webs make their burrows in moist, cool, sheltered habitats—under rocks, in and under rotting logs, some in rough-barked trees (occasionally metres above ground). They are commonly found in suburban rockeries and shrubberies, rarely in lawns or other open terrain.Australian funnel-webs are one of the three most dangerous spiders in the world and are regarded by some to be the most dangerous.There have been 27 recorded deaths in Australia in the last 100 years from spider bites. Bites from Sydney funnel-web spiders have caused thirteen deaths (seven in children).In all cases where the sex of the biting spider could be determined, it was found to be the male of the species. Most victims were young, ill or infirm. One member of the genus Hadronyche, the northern tree funnel-web has also been claimed to cause fatal envenomation but, to date, this lacks the support of a specific medical report.
Envenomation symptoms observed following bites by these spiders are very similar. The bite is initially very painful, due to the biochemical action of the venom and the size of the fangs penetrating the skin. Puncture marks and local bleeding are also usually visible. If substantial envenomation occurs, symptoms will generally occur within minutes and progress rapidly.
Early symptoms of systemic envenomation include goose bumps, sweating, tingling around the mouth and tongue, twitching (initially facial and intercostal), salivation, watery eyes, elevated heart rate and elevated blood pressure. As systemic envenomation progresses symptoms include nausea, vomiting, shortness of breath (caused by airway obstruction), agitation, confusion, writhing, grimacing, muscle spasms, pulmonary oedema (of neurogenic or hypertensive origin), metabolic acidosis and extreme hypertension. The final stages of severe envenomation include dilation of the pupils (often fixed), uncontrolled generalised muscle twitching, unconsciousness, elevated intracranial pressure and death. When death occurs it is generally as a result of progressive hypotension or possibly elevated intracranial pressure consequent on cerebral oedema.
Due to the severity of symptoms, and the speed with which they progress, in areas where these spiders are known to live all bites from large black spiders should be treated as though they were caused by a funnel-web spider. First aid treatment for a suspected funnel-web spider bite consists of immediately applying a pressure immobilisation bandage; a technique which consists of wrapping the bitten limb with a crepe bandage, as well as applying a splint to limit movement of the limb.
4.The Black Widow Spider
The Black Widow Spider is known as the deadliest spider in North America. The female of the species is a very glossy black with an hourglass present on the thorax. The hourglass mark is usually red but can range from yellowish to orange in color. The male of the species is smaller than the female and is not dangerous. The black widow spider venom is a neurotoxin. The bite of the Black Widow is not generally known to be painful at the time of the bite but the bite will swell and two small fang marks will be seen.
The symptoms of the bite are painful. The symptoms of the Black Widows bite include: localized pain in the back and abdomen, sever cramping of the abdominal muscles, nausea, labored breathing, tremors, profuse perspiration, high blood pressure, restlessness, and fever. Though most bites do not lead to serious long term side effects they have been known to lead to death.
5.The brown recluse spider
The brown recluse spider, Loxosceles reclusa, is found throughout the south central and midwestern United States.Though variable in size, adult brown recluse spiders with legs extended are about the size of a U.S. quarter. Coloration ranges from tan to dark brown, and the abdomen and legs are uniformly colored with no stripes, bands or mottling. The legs are long and thin and lack conspicuous spines. For laypersons, the most distinguishing feature of a brown recluse is a dark violin-shaped mark on its back, with the neck of the violin pointing toward the rear (abdomen) of the spider Most bites occur in response to body pressure, when a spider is inadvertently trapped against bare skin. Some people are bitten when they roll over one in bed. Other bites occur while moving stored items or putting on a piece of clothing that a spider has chosen for its daytime retreat. Brown recluse spiders have remarkably small fangs and cannot bite through clothing.
The initial bite is usually painless. Oftentimes the victim is unaware until 3 to 8 hours later when the bite site may become red, swollen, and tender. The majority of brown recluse spider bites remain localized, healing within 3 weeks without serious complication or medical intervention. In other cases, the victim may develop a necrotic lesion, appearing as a dry, sinking bluish patch with irregular edges, a pale center and peripheral redness. Often there is a central blister. As the venom continues to destroy tissue, the wound may expand up to several inches over a period of days or weeks. The necrotic ulcer can persist for several months, leaving a deep scar. Infrequently, bites in the early stages produce systemic reactions accompanied by fever, chills, dizziness, rash or vomiting.
Severe reactions to the venom are more common in children, the elderly, and patients in poor health. Persons bitten by a brown recluse spider should apply ice, elevate the affected area, and seek medical attention immediately. .