The world's largest bee species is Wallace's giant bee, also known as the giant mason bee. The females grow to be 1.5 inches long with a 2.5-inch wing span. The males are smaller and grow to a length of almost 1 inch.
Alfred Russell Wallace, who discovered the insect in 1858, described it as a large, black, wasp-like insect with immense jaws like a stage beetle." The females are known to have large mouths that are used to harvest resin to build their nests. The nests can be large, and the largest known nest as of March 2011 had 157 brood cells.