Oliarus polyphemus, the Hawai'i cave planthopper,[2] is a species of Oliarus planthopper endemic to the island of Hawai'i, where it inhabits lava tubes and crevice networks embedded in solidified lava flows.

It is thought to live primarily in a vast network of underground cooling cracks formed when pahoehoe lava from the island's various volcanoes solidified.

Due to the difficulty of surveying the primary crevice habitat, O. polyphemus is only ever encountered in these lava tubes.

[5] Olarius polyphemus relies on the roots of the ʻōhiʻa tree, which reach deep underground into the lava tubes and cooling cracks that the planthoppers inhabit.

When it is finished feeding, a nymph builds another cocoon and spend about one week transforming into an adult.