The spiders usually have a pair of poison glands in the cephalothorax. The venom is inoculated with the brackets. Its toxicity is not dependent on the size of the spider, but varies with his diet. 40 000 species recorded, a hundred have a bite that can bother the man, a dozen are really dangerous.
The Australian tarantulas of the genus Atrax is particularly dangerous. Temperament rather aggressive, they find refuge in homes after heavy rains. Fatalities are rare, but bites are always painful.
The reputation of Black Widow is not misused their venom can cause death. The effects of a bite did not manifest immediately, but after one or two hour, the victim is shaken by spasms and breathing difficulties. These symptoms are often accompanied by psychiatric disorders.
We can mention, among the species at risk, loxosceles of America and some tarantulas. Note, however, that the poison of many snakes and scorpions are generally more dangerous.
The bite of the Black Widow and the Atrax can be fatal. The tarantulas are harmless.
