There are several of these purple boxes hanging from trees in Hacklebarney State Park. The USDA is using them to check for invasive Emerald Ash Borer beetles (Agrilus planipennis), which threaten to decimate the populations of native ash trees. You can read more about the beetles here.
This photo also appears in
keyboard shortcuts: ← previous photo → next photo L view in light box F favorite < scroll film strip left > scroll film strip right ? show all shortcuts