The Hawaiian Islands have the greatest number of modern extinctions anywhere on Earth, in part because organisms on remote islands easily succumb to species introduced from other places. But the islands’ isolation also means they are home to many species found only there—including more than 500 species of fruit flies. This male Hawaiian hammerheaded fruit fly has a distinctive head with wideset eyes, a bit like a hammerhead shark’s. In a display to compete for mates, the males almost butt heads, the way bighorn sheep do—but they actually do not quite touch.

Formerly common throughout the wet, mountainside forests of the “Big Island” of Hawaii, where its larvae feed beneath the bark and on stems of several plants, this fly’s numbers have fallen dramatically. Today it lives in just one forest reserve, and researchers attribute this drop in part to the loss of its host plants due to fungal diseases. In response, in 2006 this and other Hawaiian flies were added to the U.S. federal endangered species list—providing them some needed protections.