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Tasty butterflies turn sour without toxic wingmen

Viceroy butterflies are notorious tricksters. They sport a striking pattern of orange and black nearly identical to two other species—the terrible-tasting monarch and the equally nasty queen butterfly. Birds that eat these bitter insects quickly learn to avoid them—and their convincing viceroy doppelgängers. But a new study reveals that when queens aren’t around, the viceroys themselves start to take on a terrible flavor.

Viceroys (above) and queen butterflies are found widely throughout southern Florida, where they both feed on noxious plants; only the queens were known to store the plants’ distasteful chemicals in their bodies. But viceroys also thrive in the northern part of the state, where the queens are not found. (Monarchs are comparatively uncommon in Florida.)

To find out how the viceroys protect themselves without the bitter queens, researchers chemically analyzed 80 butterflies from northern Florida and 80 more from the state’s south. Sure enough, the ones from the south had low concentrations of phenolic glycosides, chemicals similar to the ones that impart the awful taste in queens. But the viceroys from the north were chock-full of the stuff. The team then tried to feed the viceroys to lab-reared mantises, which were repulsed by the northern variety. The results suggest that without a model, the viceroys have evolved their own foul taste, the researchers report this month in Nature Communications Biology.

The finding also challenges the conventional understanding of how certain species become copycats. Often, such animals are considered harmless imitators of acrid-tasting species or just one lookalike in a set of other distasteful species. But the viceroys exist somewhere in between the two. With these duplicitous body doubles, where appearances are everything, there’s far more than meets the eye.