If you want to know the record holder for the deadliest spider in the world, then you're in the right place. The Brazilian wandering spider is considered the world's most venomous spider. Also called Banana spider, it is an aggressive and highly venomous spider found in tropical South and Central America. 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 an attack due to an excitatory effect the venom has on the serotonin 5-HT4 receptors of sensory nerves.
The amount of P. nigriventer venom necessary to kill a 20 g mouse has been shown to be only 6 μg intravenously and 134 μg subcutaneously as compared to 110 μg and 200 μg respectively for Latrodectus mactans (Southern black widow). This ranks Phoneutria venom among the most deadly to mice found in spiders.
The second most dangerous spider is the Southern black widow or Latrodectus mactans, and is a highly venomous species of spider in the genus Latrodectus. The female black widow's bite is particularly harmful to humans because of its unusually large venom glands. The bite of a male black widow is not considered dangerous to humans; it is the bite of the adult female black widow from her much larger venom sacs that has given this spider its dangerous reputation. They are well known for the distinctive black and red coloring of the female of the species and for the fact that she will occasionally eat her mate after reproduction.
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The genus Lonomia also famous for its toxicity. A typical incident involves a person unknowingly leaning against, placing their hand on, or rubbing their arm against a group of these caterpillars that are gathered on the trunk of a tree. The effects of a dose from multiple caterpillars can be dramatic and severe, including massive internal hemorrhaging, renal failure, and hemolysis. The resulting medical syndrome is sometimes called Lonomiasis.
You may notice that spiders and scorpions are not listed here, because they are not insects but arachnids. You can find the most venemous spiders and scorptions if you go back to the main menu.