Daddy-longlegs spiders (Pholcidae) - Here, the myth is incorrect at least in making claims that have no basis in known facts. There is no reference to any pholcid spider biting a human and causing any detrimental reaction. If these spiders were indeed deadly poisonous but couldn't bite humans, then the only way we would know that they are poisonous is by milking them and injecting the venom into humans. For a variety of reasons including Amnesty International and a humanitarian code of ethics, this research has never been done. Furthermore, there are no toxicological studies testing the lethality of pholcid venom on any mammalian system (this is usually done with mice). Therefore, no information is available on the likely toxic effects of their venom in humans, so the part of the myth about their being especially poisonous is just that: a myth. There is no scientific basis for the supposition that they are deadly poisonous and there is no reason to assume that it is true.
Funnel-web spiders are found in eastern Australia, including Tasmania, in coastal and highland forest regions - as far west as the Gulf Ranges area of South Australia. Thirty-six species, including three tree dwelling species, have been identified.
The Sydney funnel spider (Atrax robustus) of Australia is often quoted as being the spider with the most dangerous venom. Bites are dangerous and can cause serious illness or death. The venom appears to particularly affect primates (ie humans), whereas other mammals - such as cats and dogs - are relatively resistant.
On the other hand; according to the Guinness Book of Records the worlds most venomous spiders is the Brazilian wandering spider (Phoneutria nigriventer). The Brazilian wandering spider (Phoneutria nigriventer) is regarded by some as the most dangerous spider in the world. It is highly venomous and not reluctant to attack people who appear threatening to it. However, recent studies indicate that it only injects venom in about one-third of its bites and may only inject a small amount in another third. Thus the effects of the bites from this spider can range from only a couple of pin pricks to a full blown envenomation. The Sydney funnel-web spider apparently injects venom in every bite and may thus in effect be more dangerous --
This spider is believed to have the most active neurotoxic venom of any living spider. Its venom is so potent that only 0.006mg (0.00000021oz) is sufficient to kill a mouse.