Forget trans goats and female horses with male testicles. The hottest intersexual animal in London’s Natural History Museum is the Great Mormon Butterfly—its left half is male and its right half is female with male and female reproductive organs fused right down the middle.
The Guardian explains:
The insect, which has a 10cm wingspan, is almost black on its male side, but the female side is much paler, with clearly visible flecks of blue, red and tortoiseshell.
“It’s an amazing butterfly. The split is purely bilateral – even the colour of one side of its body is slightly different,” said Luke Brown, manager of [the museum's Sensational Butterflies exhibit]. “It has half-male, half-female sexual organs welded together. So they don’t work, it is infertile.”
Insects can be born gynandromorphs – with male and female cells – when sex chromosomes fail properly to separate when the fertilised egg divides. Around one in ten thousand butterflies is a gynandromorph. Many dual-sex butterflies probably go unnoticed, because the males and females look alike.
Brown, who has seen only two other gynandromorphs in his career, said the butterfly was feeding and flying well, and was expected to have a normal life expectancy of around one month. The specimen will become part of the museum’s lepidoptera collection.
In 2008, a half-male, half-female moth emerged at the museum. The insect had one bright yellow wing and another that looked brown and dusty. Crabs and lobsters can also be gynandromorphs.
Of course, other intersex animals exist as well (including humans). Drawing attention to these other creatures help us appreciate and understand human intersexuality as well.