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Yes there are quite a few spiders which can cause death if they bite a human being, at least if these bites go untreated. There are over 40,000 species of spiders in the world and almost all of them are venomous but only a few of them can actually kill a human being with their bites. There are basically 4 genera of spiders which have some species which can actually kill human beings with their bites and they are ;

1. Widow spiders: The widows of genera Latrodectus have about 32 species and they are mostly found in the US. Out of these 32 species only two which are called the black widows have venom which can actually cause death in human beings. Antivenoms exist for such bites so incase you actually get bitten by one of them you should be ok.

2. Brown Recluse spiders: These spiders belong to the genera Loxosceles. Their bites aren't quite as fatal as widow spiders but they can actually kill human beings. They are often found in North America and South America. They are deadlier than widows because as of now the only antivenoms that exist for them is only in Brazil, so if you get bitten by one anywhere else, just pray that a Brazilian who happens to be passing g by with the antivenom shows up.

3. Funnel web spiders: These spiders belong to the the Attrax genera and are apparently the most deadly of all spiders. Their bites can actually send a human being to the afterlife in less than 24 hours if untreated. They are primarily located in Australia.

Brazilian wandering spider: This spider belongs to the genera phoneutria and is only found in Brazil. Rest assured that even if you go to Brazil you won't encounter one because they are mostly found deep in the rain forest. I'm not entirely sure if an antivenom exists but for your own safety, stay out of the Amazon rainforest.

Spiders are eight-legged animals that are feared by almost everyone. As arthropods in the Arachnida class, spiders are invertebrates that have exoskeletons and are segmented with jointed bodies and legs.

Not only that, the spider also has surprising things that you may not know. Anything? from about.com, following facts about spiders.

1. Build a giant net

Some spiders can build giant webs if they stay in the same location for a long time.

For example, as a result of flooding in Pakistan in 2010, millions of spiders fled to trees trapped by flood water. A number of large trees also turn into a cocoon of spider webs because it takes a long time for flood water to recede.

Arachnologists and entomologists believe that giant nets can also be made as a result of the ballooning phenomenon. This occurs when young spiders begin to immigrate from one place to another. During the ballooning phenomenon, the spider will rise in height, with the stomach pointing up and releasing the silk thread into the air.

2. Some spiders are cannibals

Cannibalism is sometimes seen in spiders when food sources are scarce. There is a spider species that is willing to sacrifice itself to be eaten by a young spider that has just been removed from the egg. However, in most cases, cannibalism occurs in sexual relations.

Female spiders will eat sex partners (male) either before or after mating. Researchers from Miami University in Ohio have found that the size of a male spider will determine whether it will be eaten or not by a female spider.

Studies show that in one species of spider, Hogna helluo, male spiders smaller than females have an 80 percent chance of being eaten.

3. Spiders cannot be trapped in their nets

Researchers from the Smithsonian Tropical Research Institute and the University of Costa Rica believe that spiders have hair on the legs by producing non-stick-free substances so they can stick to their webs.

The results of the study also found that during the process of making nets, spiders reduce their adhesive strength by strategically moving their feet along the net.

4. Spiders use electrostatics to catch their prey

Researchers from Oxford University have found that electric nets in spiders play a role in capturing insects and particles in the air.

The spider webs are coated with substances such as glue that have electrostatic properties which cause the net to pull all charged particles and stick to objects in the air. Because every object that moves through the air develops static electricity so that the net can attract them.

Spider webs can also be used to track pollutants such as pesticides, because these particles become trapped in the net too.

5. Spider spider is expected to be a medicine one day

The researchers found a protein in poison tarantula rose in Chile that is being used to develop drugs that can counteract the adverse effects of muscular dystrophy or muscle disease.

In research conducted with mice, this protein was able to prevent muscle cells from worsening, allowing mice to gain strength.

Individuals with muscular dystrophy have a defect in muscle protein that causes the inability of muscle cells to maintain their shape. According to the researchers, this causes the ion channels in the cell to remain open leading to break down muscle tissue. In the study, spider venom proteins were able to maintain closed ion channels and suppress symptoms of disease.

Yes, they are the ones designated as poisonous within the species and if bitten and enough venom is injected ,they can cause death