Phalacrognathus muelleri, colloquially the rainbow stag beetle, is a species of beetle in the family Lucanidae. It is found in northern Queensland, Australia and New Guinea.
Phalacrognathus muelleri has been the official symbol of the Entomological Society of Queensland since 1973.
This species is commonly known as golden, rainbow, magnificent, Mueller’s and king stag beetle. In 1885 the species was named Phalacrognathus muelleri by Sir William Macleay in honour of Baron Ferdinand von Mueller, the Victorian Government Botanist, the genus Phalacrognathus created at the same time.
Males of Phalacrognathus muelleri are the largest members of the Lucanidae family in Australia. Males range from 24 mm to 70 mm (0.9 to 2.8 in) in length, whereas the smaller females range from 23 mm to 46 mm (0.9 to 1.8 in). source