An Oregon-based environmental group yesterday petitioned the federal government to list seven species of Hawaiian yellow-faced bees as endangered.

The Xerces Society for Invertebrate Conservation wants the U.S. Fish and Wildlife Service to protect the species because they are in "imminent danger" of extinction.

The Portland, Ore.-based society contends the bees are critical pollinators of many endangered Hawai'i plants, and the bees' decline could lead to the plants' extinction. It also asserts protection of the bees could lead to recovery of the plants.

The tiny yellow-faced bees, which grow to about a half-inch long, are Hawai'i's only native bee species. They live on all Hawaiian Islands and in varying environments, including coastlines, dry and wet forests, and shrublands.

The seven species are: Hylaeus anthracinus, Hylaeus longiceps, Hylaeus assimulans, Hylaeus facilis, Hylaeus hilaris, Hylaeus kuakea and Hylaeus mana.

The Fish and Wildlife Service is likely to respond to the society's petition in about a year, said Scott Hoffman Black, executive director of the society.