When the weather gets muggy, iridescent bees shift their metallic hue.
The insects are a rich blue-green when ambient humidity is low. But as the amount of moisture in the air increases, the bees turn a coppery green, researchers report April 22 in Biology Letters. The reversible mood ring–like effect may be an overlooked phenomenon determining day-to-day color in bees and other insects.
Many bees have a shimmery exoskeleton. Some researchers working with specimens in museum collections have noted it changes color. For instance, the bees appear to dramatically shift color when placed in a high humidity chamber used to make them more flexible for mounting and imaging.