The photo shows insects crawling across a white sheet in the Arizona wilderness. It’s nighttime and the sheet is illuminated with light, attracting critters that populate the Chiricahua Mountains—green stink bugs, sphinx moths, and others. To most of us, the photo appears to capture a menagerie of life. To scientists, it represents loss: Years ago in these mountains, you’d find many more species of insects, and rarer ones, crawling across the sheet. They’re gone now.

The photograph, by David Liittschwager, is a snapshot of a mass insect decline that’s reverberating across the globe. National Geographic photo editors chose it as one of our 26 best animal photos of the year.

Many of the chosen photos feature species that aren’t commonly seen,