This species was named by Broun in 1904 as Prodontria Lewisii, from "three mutilated individuals found by Mr. J. H. Lewis on the sand-hills of the Molyneaux River.

This large beetle has pale reddish-brown elytra which are strongly convex and with deep groves passing along their length.

Some of the beetles were found north of the town in 1968, next to a nine-hole golf course, but that population was destroyed when the course was expanded to 18 holes.

[7] Much of the rest of the beetle's original 500-hectare range was destroyed by the construction of the Clyde Dam in 1979 and the subsequent formation of Lake Dunstan.

[5] In 1996, after years of being classed as Vulnerable, the Cromwell chafer was declared Critically Endangered on the IUCN Red List.

Redback spiders shelter in rabbit holes in the reserve, and may kill hundreds of chafer beetles a year.