LOS ANGELES (AP) — Activists plan to sue the U.S. government, claiming it's failed to protect a nearly-extinct fly in California's agricultural heartland.

The Center for Biological Diversity filed notice Thursday that it will sue the U.S. Fish and Wildlife Service.

The species at issue is the San Joaquin Valley giant flower-loving fly. It's about 1½ inches (38 millimeters) long and once lived in sandy areas throughout the valley. But activists say it now survives in just one population about 15 miles east of Bakersfield and that group is under threat from sand mining.

The Fish and Wildlife Service was petitioned in 2014 to list the fly as endangered.

The Center for Biological Diversity says the agency determined in 2015 that such protection might be warranted but has done nothing since then.