Heaviest arachnid

The world's heaviest species of arachnid is the goliath bird-eating spider Theraphosa blondi, native to the coastal rainforests of Surinam, Guyana, French Guiana, southern Venezuela, and northern Brazil. A two-year-old specimen of this species, bred by Robert Bustard and reared by Brian Burnett of Alyth, Perthshire, in Scotland, UK, weighed 170 g in February 1998.

Apart from various spider species, the heaviest arachnids are certain scorpions, most notably the imperial scorpion Pandinus imperator from West Africa. Adult female specimens of this very impressive species can weigh up to 60 g when pregnant.

It can also measure up to 20 cm in length – the same average length as the hand of an adult human being.