What is a swamp adder?

The swamp adder, scientifically known as the Proatheris superciliaris, according to Biodiversity Explorer, is a venomous type of viper that lives in Central Mozambique. It was featured as the most venomous snake in India in a Sherlock Holmes story, "The Adventure of the Speckled Band," but the story is fictitious.

The swamp adder feeds on frogs, toads and small rodents and is native to East Africa. It is identified by its grey-brown or reddish-brown coloration and the three rows of brown spots and yellow lines that run down the length of its body. It also has a yellow or orange-tipped tail, according to Biodiversity Explorer.