What are the Most Dangerous Spiders in the World?

The Most Dangerous Spiders in the World Include:

Brazilian Wandering Spider

Brazilian wandering spiders, Phoneutria fera and Phoneutria nigriventer, have been considered the most venomous spiders in the world. Hundreds of bites are reported annually, but a powerful antivenom prevents deaths in most cases. These species of spider are also referred to as banana spiders because they are frequently found on banana leaves. They have an aggressive defense posture, in which they raise their front legs straight up into the air. Their venom is toxic to the nervous system and causes symptoms such as salivation and irregular heartbeat.

Sydney Funnel Web Spider

The Sydney funnel-web spider, Atrax robustus, is one of the most dangerous spiders to humans in the world. Native to Australia, this poisonous spider is found in moist habitats such as under logs or in gardens. The Sydney funnel-web spider has a venom potency of 0.2 mg/kg as a lethal dose for humans. The female spider is four to six times less venomous than the male. An antivenom was developed in 1981, so a bite from this spider likely will not cause death if medical help is available to quickly administer the antivenom.

Black Widow Spider

These spiders can be found worldwide and are most recognized for the red hourglass shape on the underside of their abdomen. Although fatalities are rare, the black widow’s venom is reported to be 15 times stronger than a rattlesnake’s and can cause muscle aches and nausea, as well as make breathing difficult. Black widow webs are built in sheltered environments, irregularly shaped, and located near ground level.

Brown Recluse Spider

The brown recluse spider, Loxosceles reclusa, is found throughout the South, Central, and Midwestern United States. These spiders are widely over-reported and less common than perceived. Likely hiding places include crevices, corners, attics, storage areas, ceiling voids, wall-floor junctures, and especially behind clutter and stored items. Brown recluse spiders are difficult to eradicate, largely because of their secretive habits. Virtually any dark, undisturbed area can serve as a habitat, and many such places occur within buildings. Because of this (and the potential health threat), brown recluse spider treatment is best performed by professionals.

Most brown recluse spider bites occur in response to body pressure when a spider is inadvertently trapped against bare skin. Some people are bitten when they roll over a brown recluse 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 very small fangs and cannot bite through clothing. Someone bitten by a brown recluse spider should apply ice, elevate the affected area, and seek medical attention immediately.

Redback Spider

The redback spider, Latrodectus hasselti, is also native to Australia. The females are venomous and have an orange or red stripe on the back of their abdomen. Males are shorter-lived, surviving several months to the females’ two or three yearlong lifespans. People bitten by female redback spiders can experience localized pain and swelling. General symptoms include nausea, vomiting, restlessness, and increased blood pressure. Severe cases may also involve respiratory failure. Severe reactions may be prevented with antivenom.

Brown Widow Spider

The venom of a brown widow, Latrodectus geometricus, while seldom life-threatening, produces very painful effects including muscle spasms, ‘tetanus-like’ contractions, and, in some cases, spinal or cerebral paralysis. This paralysis is generally temporary but might leave permanent damage to the central nervous system. A serious bite will often require a short hospital stay. Children, the elderly, and immunocompromised individuals are at the most risk of serious effects. Brown widow spiders live outdoors under rocks, logs, woodpiles, and debris. This spider is also well adapted to living indoors in protected places. The bite of a brown widow spider is minor in comparison to that of a black widow because the brown widow does not have and cannot inject as much venom as a black widow.