Ants have the largest brains in proportion to their bodies. A single ant brain has about 250 000 brain cells, so a colony of 40,000 ants has the same number of brain cells as a human being. The ant queen lives up to ten or even twenty years, while the life expectancy of an average ant is about 45-60 days. Although there are species of ants that grow up to 2cm (0.8 inches), normal ants are from 2 to 7 mm (0.1-0.3 inches) long. Having this in mind, it is quite difficult to imagine that ants are about 1/10 of the total animal tissue in the world.