Approximately 25 spider species possess venom that can cause illness in humans. Of these, three have been deemed medically significant.

These spiders inject venom through fang-like appendages known as chelicerae. Their bites can be dangerous, especially for children and immunocompromised individuals. They typically produce a venom with neurotoxic effects. Click the Poisonous Spiders In Kentucky to learn more.

The black widow spider, Latrodectus mactans, is the most dangerous of all North American spiders. Females can range in color from dark brown to black, and have a distinctive hourglass mark on the underside of their abdomens. They are found in many of the same places as other spiders—under logs, bushes, rocks, sheds, garages, and basements, among other places. Because of this, they are commonly encountered in the United States by people who work outside, especially those who remove woodpiles or other outdoor debris.

The widow’s venom contains a neurotoxin that causes muscle pain, which starts at the bite site (often on a hand or foot) and then spreads to other parts of the body, such as the chest and abdomen. The pain is so severe that some people mistake it for appendicitis or a heart attack.

If bitten, seek medical help immediately. Symptoms usually start within a few hours, and may include pain, sweating, nausea, vomiting, cramping, and a target-shaped red area at the bite site. If the bite is on the upper part of the body, most people will feel the pain in their chests.

Black widows typically bite only when they are disturbed. Therefore, it is important to keep garages, sheds, and other storage areas clean. This will also help eliminate the places where they like to hide, such as woodpiles and rock walls.

A black widow’s poison is injected into its prey by using tiny punctures it makes in the victim’s skin. It then injects a venom that paralyzes the victim and eventually kills them. The poison may also cause rhabdomyolysis and elevated creatine kinase levels in the blood.

If bitten, wash the bite area thoroughly with soap and water. A tetanus shot should be given as soon as possible. Antivenin is available for severe cases, but doctors are cautious about using it because of the side effects, including rhabdomyolysis and lowered blood pressure. A new antibody-based antivenom is being developed that is expected to have fewer side effects.

Brown Recluse

Although the Brown Recluse is one of the most dangerous spiders, bites are relatively rare. Like many spiders, it delivers venom to subdue and digest its prey. Unlike other North American spiders, however, the Brown Recluse delivers its venom through a bite that is generally not felt.

These spiders can be distinguished by their segmented body, the dark markings on their cephalothorax (the region between the head and abdomen) that resemble a fiddle or violin, and their ability to climb. They are tan to a light brown color and have six eyes.

In the wild, they prefer dark sheltered places such as under porches, in woodpiles and among rocks and shrubbery. They may hitch rides on objects and enter homes through crevices, cracks in foundations and around doors, vents, windows and eaves. Inside, they may hide in cluttered storage areas and closets, under furniture, folded clothing and blankets and other clutter.

The venom of the Brown Recluse produces a variety of reactions in people. Some are unaffected, others experience immediate or delayed effects as the venom destroys tissues at the bite site. In some cases, the area of the bite becomes a blistered lesion that is characteristically affixed to the skin and has a pronounced red center. The bleb eventually darkens and ulcerates to form a scar. Some patients develop a fever, chills, sweating and a general feeling of sickness and discomfort. In the most serious cases, symptoms include coma, fluid in the lungs (pulmonary aspergillosis), blood in urine and the whites of the eyes turning yellow (jaundice).

If you have a reaction to a Brown Recluse bite, it is important to wash the affected area thoroughly. It is also a good idea to keep the telephone number of your regional poison control center handy so you can contact them for further advice and guidance.

Until a medical professional has examined the affected area, a person should be careful not to touch or disturb the wound. This is because the venom can cause tissue necrosis or cellulitis if it becomes infected. First aid consists of elevating the bitten area above heart level, cleaning with soap and water, and ensuring the patient’s tetanus immunization is up to date. NSAIDs can be used for pain management and patients with severe bites may require opioid medication.

Redback Spider

The redback spider is a very dangerous species of spider that lives in Australia. It is known to kill and injure many people each year. However, the number of deaths has been significantly reduced since antivenom was developed in 1956. This spider is not migratory and generally remains in one hunting ground for most of its life. It hunts insects and other small creatures that become ensnared in its untidy webs in warm sheltered locations, commonly near or inside human dwellings.

Males are considerably smaller than the female and can be recognized by a red stripe with white spots on the top of their abdomen or by a red hourglass-shaped marking beneath it. They may also have pairs of short triangles on their sides.

These spiders have evolved in a variety of habitats including savanna, temperate, tropical and desert regions but are adapted particularly well to living with humans. This adaptation has probably been aided by their ability to survive in the warm shelters of our homes and workplaces, which they tend to inhabit during the cooler months. Breeding takes place all the year round, but peaks during summer. Males will fight over the rights to mate with a particular female, often fatally so. The females are cannibalistic and will eat the defeated male shortly after mating.

The male’s unique approach to mating is a spectacular display of courtship, which includes vibrating his body and tapping on the female’s web with his front legs. The male then somersaults to position his abdomen over the female’s mouthparts. The female then consumes the much smaller male. This is a very dangerous behaviour and should be avoided at all times.

Bites from the redback are a very serious hazard and require immediate medical attention. Victims will experience extreme pain at the bite site. In addition, local swelling and gooseflesh will develop within an hour. After about 24 hours the syndrome will progress to systemic envenoming, causing sweating, malaise, abdominal or chest pain, tremor, headache, fever and possibly pulmonary edema.

It is uncommon for the bite of a redback to be fatal, but death has occurred in cases where the victim was very old, young or sick and had no access to antivenom. Although the spider is a predator, it will not attack humans unless provoked and can only bite as a defence mechanism when approached.

Longhorn Spider

Despite the fearsome reputation it has garnered in some circles, this spider is among Nature’s most remarkably beautiful creations. The visual splendor of this creature is heightened by its stunning camouflage, which serves to protect it from predators and prey alike.

The Longhorn Spider, or Macracantha arcuata, is a spiny, orb-weaver spider that can be found in fields and forests. It’s also commonly referred to as the Curved Spiny Spider or the Long-Horned Orb Weaver. Professionals, however, tend to use its formal scientific name, which was given by Danish zoologist Johan Christian Fabricius in 1793.

This orb-weaver, like most members of its family Araneidae, builds wheel-shaped webs that can be found in gardens, fields, and forests. It is a venomous species, but its venom isn’t powerful enough to kill a healthy human. Most orb-weaver bites are painless and cause no serious injuries to humans.

Like other orb-weaver spiders, the Longhorn Spider injects enzymes into its prey along with venom to break down internal tissues and make it easier for the spider to digest its meal. Additionally, orb-weaver spiders may also inject cytotoxins into their prey to damage cells and tissues around the bite site.

Male orb-weaver spiders exhibit a striking pattern of red and black. This coloration helps them attract females by resembling insects that can sting, such as wasps and flies. This is an example of Batesian mimicry, where a harmless or helpless species benefits by resembling a predatory or harmful species.

As with all orb-weavers, the Longhorn Spider primarily hunts small insects. Its venom is designed to paralyze the nervous system of its prey, which allows it to quickly and efficiently consume its meals. This spider’s chelicerae and fangs align and hinge parallel to the body axis, which is unique among spiders.

This incredible spider is a magnificent sight to behold, but it shouldn’t be mistreated or handled. The good news is that fewer than 30 people have died of a spider bite in the United States since records began. This is in part due to the fact that orb-weaver spider venom attacks insects, not people. Nevertheless, this spider’s habitat loss is a significant threat to its continued survival.