Here is my male specimen of Chiasognathus grantii (Stephens)/1832. It is one of seven species belonging to the genus Chiasognathus.
Charles Darwin collected the species in Chile during the second voyage of HMS Beagle, and despite the enlarged mandibles of the males he noted that the jaws were "not so strong as to produce pain to finger".
Apparently, this species is an active climber in Nothofagus forests; also known as the southern beeches. It's noted for climbing many meters up high whilst searching for females. Males are said to be very combative and large males of opposing mandible (size) may joust at length to get the "better" of an opponent.
Though the species is a common fixture in most beetle collections of any breadth; I still find it a most unique and intriguing looking lucanid in it's own right !
This is a quite large male specimen of the species so I accorded it a "life-like" natural posture to enhance its threatening appearance.