Many butterflies have “tails” on their hindwings. This small Blue at Koshi Tappu in Nepal is a good example:
When its wings are closed it looks like this:
One hypothesis is that the combination of these long wiggly protuberances and the eye spots at their base mimics the antennae and eyes of a butterfly’s head. A predator is then confused, and instead of attacking the head it goes for the much less important hindwing. Mind you, a butterfly whose wings have chunks missing probably won’t fare so well either.
Here is an entirely different Nepalese butterfly, with similar wiggly tails, though the eye spots, at least on the upper side, are not so obvious.:
And this one in Ecuador has gone overboard:
Since Darwin’s day, eye spots on butterflies have been thought to pay a role in confusing predators (and attracting mates). Butterflies and moths can have eye spots without fake antennae, as this Grand Paon de Nuit (Grand Peacock of the Night) , Saturnia pyri, near Carcassonne, France, so dramatically displays:
They can also have fake antennae without eyespots, as this Swallowtail butterfly in Maine shows:
In 1980, scientists from the Smithsonian showed that the more “false head” features a butterfly had, the more likely it was to be attacked on that part of the wing, so apparently deception works!
* Janus was the Roman god of beginnings and endings, the past and the future, and he was always depicted with two faces. He is also associated with deception, which is why I chose his name for my title. I am not the first person to think of this link. This moth’s scientific name is Automeris janus:
(Thanks to the lepbarcoding.org website for this photo. The URL refused to copy, so I hope the unnamed photographer will forgive my use of this photo.)