Edward Donovan described the King Christmas beetle in 1805 as Melolontha viridi-ænea, writing, "Nature seems to have devoted abundant attention to the embellishment of this common insect: its glow of colouring is peculiar and inimitable.

The prevailing hues do not strictly please us by their harmony as their contrast, which is indeed striking, or rather glaring, but upon the whole produce a rich effect", describing it as "testaceous" (red-brown) overlain with translucent green and a brassy-gold sheen in light.

The King Christmas beetle was described in 1817 as Rutela caesarea by Gustaf Johan Billberg and R. latreillei by Leonard Gyllenhaal.

The pygidium, coxae, and abdomen are a bright green, while the legs are red-brown, and tarsi are black.

[2] The King Christmas beetle has been recorded on the turpentine tree (Syncarpia glomulifera) of the family Myrtaceae.