Hawaiian yellow-faced bees

A number of Hawaiian yellow-faced bees (Hylaeus species) endemic to the Hawaiian Islands are threatened with extinction. These bees are important pollinators of native Hawaiian plants, many of which are also endangered and the decline of these bees might lead to the loss of native plants. Alternatively, protection of these pollinators could aid the recovery of the endangered plants.

In order to gain protection for Hawaiian yellow-faced bees and the habitats upon which they depend, The Xerces Society has petitioned the US Fish and Wildlife Service in 2009 to protect seven of the most at risk species under the U.S. Endangered Species Act. The petitioned species include: Hylaeus anthracinus, Hylaeus longicepsHylaeus assimulansHylaeus facilisHylaeus hilarisHylaeus kuakea and Hylaeus mana. On September 30, 2015, the US Fish and Wildlife Service proposed to list all seven of these species as Endangered Species.

In the late 1800s and early 1900s, the biologist R.C.L. Perkins called Hawaiian yellow-faced bees “almost the most ubiquitous of any Hawaiian insects.” By surveying many of Perkins’ original collecting locations, biologist Karl Magnacca has demonstrated that most Hawaiian yellow-faced bee species are in decline, many are extremely rare, and several are possibly extinct.

Hawaiian yellow-faced bees can be found in a variety of habitats on the Hawaiian Islands, including coasts, dry forests and shrublands, mesic and wet forests, and subalpine shrublands. All Hawaiian yellow-faced bees strongly depend on an intact community of native plants and are mostly absent from habitats dominated by non-native plant species. These bees require a habitat with a diversity of plants that flower throughout the year so that a consistent source of pollen and nectar is available. Many species nest in the ground, but some nest in hollow stems of plants; the availability of nest sites is another important habitat requirement for these animals.

Hawaiian yellow-faced bees are threatened by development (especially in coastal areas), fire, feral ungulates such as pigs, invasive ants, and the loss of native vegetation to invasive plant species. Because remnant populations of many species of Hawaiian yellow-faced bees are small and isolated, they are especially vulnerable to habitat loss, predation, stochastic events, and other changes to their habitat. Conservation of these important pollinators will require the active management of natural areas where populations are known to exist.

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