The Mount Hermon June Beetle is a large, white-lined June beetle, found exclusively in sandy soils in the Santa Cruz Mountains. In particular, the beetle is only known from a formation known as the Zayante Sand Hills, which also supports a threatened grasshopper and several threatened plants.

Larval Polyphylla barbata spend up to three years underground feeding on plant roots. The adults have a relatively short activity period, being mainly concerned with finding a mate and, if female, a suitable place to lay her eggs.

Several factors threaten the habitat on which these beetles depend. The most significant has been urbanization of the area. On top of being naturally very restricted, as much as 60% of the sand hills habitat has been built on or paved over. Much of the remainder has been mined for sand or is subject to heavy recreational traffic. Furthermore, fire supression has led to significant alteration of the vegetation of the sand hills, with the fire-tolerant pines and cypress being displaced by less tolerant species.

A couple of recent grants from the Fish and Wildlife Service have permitted the purchase and protection of large tracts of sand hill habitat. This is an encouraging development, though many management challenges remain before this beetle's future can be considered secure.