Geodorcus sororum is a large flightless species of stag beetle in the family Lucanidae. It was discovered in 1973 by Mr. A. Wright on an expedition to Middle Sister Island/Te Awanui, one of The Sisters Islands/Rangitatahi which are part of the Chatham Islands in New Zealand. This holotype specimen is held in the New Zealand Arthropod Collection. It is considered one of the rarest and most valuable species of Lucanidae. It was first described by Beverley Holloway in 2007. The name sororum is translated from Latin to mean "belonging to the sisters".

...