The natural world sometimes seems like one big costume party. In it, animals pretend to be someone they are not, blend in with their surroundings or employ some element of disguise which enables them to escape detection when they are in danger of being hunted. As many predators like birds hunt mainly by sight, disguises go a long way in avoiding being made a meal of. These masters of disguise have perfected their art through generations, with species that are better at being elusive increasing in numbers and those that were unsuccessful in hoodwinking their predators declining.
One such trickster is a family of butterflies called Lycaenidae. Many of these butterflies have evolved brightly coloured spots on the underside of their hind wings, with two tails extending from the tips of the wings- fake eyes and fake antennae. The spots on the hind wings are usually so brightly coloured that they can easily be mistaken for the real head of the butterfly.
Why would having a fake head help these butterflies? You might ask.
The answer is that it helps them narrowly avoid death. Birds and lizards like to eat butterflies head first (some say this is in anticipation of the direction that the prey will fly off in). With their showy “heads” on the rear of their wings, Lycaenid butterflies can fly away to safety with just a portion of their hind wings clipped off by the birds.
I found this pretty Pea Blue (Lampides boeticus) butterfly in Bangalore and exclaimed excitedly since it was the first time I had come across a fake head after reading about it.
The fake eyes of this butterfly have a beautiful, metallic blue dot on the corner. It meditated on my finger for a little while before flying away, possibly disgruntled that I was subjecting it to so much scrutiny.
As if a fake head were not crafty enough, Lycaenid butterflies have evolved various behavioural adaptations to add further believability to the heads on their rears. Some turn around 180 degrees on landing and walk backwards, to further confound their predators regarding its real head. Others raise the rear end of their wings and lower their real heads- making them even more inconspicuous, and some scissor their hind wings to draw more attention to their posterior.
Some scientists proposed that fake heads in butterflies may also serve to deter predators when looked at in three dimensions- when sensing danger, some Lycaenid butterflies turn around so that their rear faces the predator, and opens and closes a portion of their wings. This creates the illusion of an ominous mouth opening and closing, as though contemplating a tasty meal.
Butterflies in general are excellent illusionists. Some species have large ‘eye-spots’ on the upper parts of their hind wings which they suddenly open when they feel threatened, to alarm a predator. The eye-spots are also thought to give the illusion of the butterfly being a much larger animal.
Another example of great cunning is in butterflies that have evolved to resemble distasteful butterflies. One such example is the female Great Eggfly, which resembles the foul-tasting Common Crow (a butterfly). Birds remember butterflies that did not make a tasty meal. By mimicking the Common Crow, the female Great Eggfly escapes being caught.
You might wonder why all butterflies do not employ some cunning feat that helps them survive. It is because there are several contending forces in play during natural selection- such as traits that make an individual more attractive and helps them find a mate. Finally it is only those characteristics that help a species survive and sustain itself that are passed on to the next generation.
What of the birds- those predators of butterflies? Are they to be made a fool of, time and again? Ol’ natural selection kicks in here too. Just as butterflies which evolve ways to escape detection, birds may evolve a sharper sense of discrimination in a case of co-evolution.
So the natural world is not only just a big costume party, but also a never-ending race between predators and prey to get the upper hand.
(An edited version of this post was published on The Alternative)