B. Smith ex Wallace, 1869
Megachile pluto is a very large Indonesian resin bee (a leafcutter bee that uses resin to make compartments in its nest). Females can be as large as 38 mm (1.5") long with a wingspan of 63,5 mm (2.5"), Megachile pluto is regarded as the largest bee in the world, and has been referred to as Wallace's giant bee. Males only grow to about 23 mm (0.9") long.
Megachile pluto was first discovered in Indonesia in 1858 by the naturalist Alfred Russel Wallace. It was thought to be extinct until it was rediscovered in 1981 by Adam C. Messer, an American entomologist, who found six nests on the island of Bacan and other nearby islands.
These bees build their nests inside active termite nests, which explains why even island residents were unaware of their existence.
Messer, A. C. (1984). "Chalicodoma pluto: The World's Largest Bee Rediscovered Living Communally in Termite Nests (Hymenoptera: Megachilidae)". Journal of the Kansas Entomological Society 57 (1): 165–168. JSTOR 25084498.