Lachesis is a genus of venomous pitvipers found in remote forested areas of Central and South America. The generic name refers to one of the Three Fates in Greek mythology who determined the length of the thread of life. Three species are currently recognized.
Adults vary in length from 2 to 2.5 m (6.5 to 8.25 ft), although some may grow to as much as 3 m (10 ft). The largest known specimen was just under 3.65 m (12 ft), making it the longest venomous snake in the Western Hemisphere. This is also the longest viper in the world. Although they are not the heaviest vipers, being surpassed in mass by the gaboon viper and the Eastern diamondback rattlesnake, large adults still commonly weigh up to 3 to 5 kg (6.6 to 11 lb). The bushmaster's tail ends with a horny spine which it sometimes vibrates when disturbed in a similar manner to rattlesnakes. This led to some calling it 'the mute rattlesnake'.
