Spiders are active hunters and rely heavily on their bites to paralyze and kill their prey before consuming it. They also bite in self-defense.Though all tarantulas are venomous, so far there is no record of a bite causing a human fatality, though some bites cause serious discomfort that might persist for several days. Despite their often threatening appearance and reputation, no tarantula has been known to have a bite that is deadly to humans. In general, the effects of the bites of all kinds of tarantula are not well known. While the bites of many species are known to be no worse than a wasp sting, accounts of bites by some species are reported to be very painful and to produce intense spasms that may recur over a period of several days; the venom by the African tarantula Pelinobius muticus also causes strong hallucinations.[13] In all cases, it is advisable to seek medical aid. Because other proteins are included when a toxin is injected, some individuals may suffer severe symptoms due to an allergic reaction rather than to the venom. Such allergic effects can be life-threatening.