A female’s egg sometimes has two nuclei, a Z and a W. When they’re “double fertilized” by a male’s Z sperm, Jahner says, the resulting embryo is half each sex. How rare are these specimens?

An extremely rare half-male, half-female bird has been caught on camera. It is only the second example recorded in over 100 years of a wild Green Honeycreeper with both distinct half-green ...

a half male half female butterfly. The butterfly species is common in North America. However, its sex is incredibly uncommon. The scientific term for this phenomena denotes the butterfly a ...