Australian funnel-web spiders are one of the most medically significant groups of spiders in the world and are regarded by some to be the most deadly, both in terms of clinical cases and venom toxicity. Six species have caused severe injuries to human victims: the Sydney funnel-web spider ("Atrax robustus"), the northern tree-dwelling funnel-web spider ("H. formidabilis"), the southern tree-dwelling funnel-web spider ("H. cerberea"), the Blue Mountains funnel-web spider ("H. versuta"), the Darling Downs funnel-web spider ("H. infensa"), and the Port Macquarie funnel-web spider ("H. macquariensis").