Blue Moon Butterfly aka The Great Eggfly (Hypolimnas bolina)

I clicked this butterfly while waiting at Vijaynagar, Indore for my nephew’s son to arrive from school. I found the butterfly hovering over lantana bush growing wild in an empty plot.
The Blue Moon Butterfly is a black-bodied butterfly displaying conspicuous sexual dimorphism. The male has jet black wings dotted with two pairs of prominent white spots on the forewings and one pair on the hindwings.
The female of the same species looks drastically different and mimics a poisonous species of another type of butterfly. As a matter of fact, the female is a mimic with multiple morphs. The upper side of the female wings are brownish black in color and unlike the wings of the males, do not have any white spots The edges have white markings which are very similar to a poisonous species of butterfly called Common Indian Crow.
This is a case of Batesian mimicry, where a harmless species mimics the warning signals of a harmful species for protection.
The Blue Moon should be called Once in a Blue Moon Butterfly, because the males were almost wiped off a few years ago due to a bacterial infection.
In fact, the species made international headlines a few years ago, when the male butterflies in the South Pacific Samoan islands were nearly wiped off by an invasive bacterial species, leaving an alarmingly low male to female sex ratio 1:99. However, the males have staged an amazing comeback by evolving resistance to the parasitic bacteria. This is a prime example of one of the fastest evolution at work, something that happens only once in a blue moon.

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