Hylaeus hilaris

Hylaeus hilaris was added to the United States endangered species list in 2016 due to its extreme rarity and the ongoing threats to its native Hawaiian habitat. The species is endemic to Maui Nui, meaning it exists nowhere else in the world.

A cleptoparasitic bee does not build its own nest but instead lays its eggs in the nests of other bee species, where its larvae feed on the host's pollen provisions. Hylaeus hilaris follows this parasitic lifestyle, making it directly dependent on the survival of its host bee species.

Hylaeus hilaris is endemic to Maui Nui, the Hawaiian island group that includes Maui, Molokai, Lanai, and Kahoolawe. Its extremely limited geographic range is a key factor contributing to its endangered conservation status.

The primary threats include habitat loss from development, invasive plant species that replace native Hawaiian flora, and introduced predators such as ants and wasps. These pressures have contributed to its listing under the U.S. Endangered Species Act alongside several other Hawaiian yellow-faced bee species.