A museum exhibit volunteer at Drexel University got an incredible surprise last fall, when he came upon a half-male and half-female butterfly just emerged from its chrysalis.
Chris Johnson, a volunteer for the university's Academy of Natural Sciences, was working on an exhibit called Butterflies! in October when he noticed a brand-new butterfly slowly opening up its wings.
The butterfly's two right wings were brown, with white and yellow spots, while the left wings were darker, with blue and purple markings.
"The wings were so dramatically different, it was immediately apparent what it was," said Johnson in a statement. The volunteer was looking at a butterfly that was exactly half female and half male.
"I thought: 'Somebody's fooling with me. It's just too perfect,'" Johnson added.
The butterfly was determined to be a Lexias pardalis, and its condition is called bilateral gynandromorphy.
"Gynandromorphism is most frequently noticed in bird and butterfly species where the two sexes have very different coloration," Entomology Collection Manager and lepidopterist Jason Weintraub explained. "It can result from non-disjunction of sex chromosomes, an error that sometimes occurs during the division of chromosomes at a very early stage of development."
While scientists know the condition is very rare, it's not easy for them to gauge just how rare, because gynandromorphism can often be overlooked in species whose males and females look similar to each other.
The butterfly Johnson encountered came to the university in a shipment of pupa from a sustainable butterfly farm in Malaysia. Lexias butterflies, which don't have a standard colloquial name but are known as "brush-footed" butterflies, live in Southeast Asian rainforests.
The special half-and-half butterfly has been preserved and pinned and will be displayed at Drexel's Academy of Natural Sciences from Saturday, Jan. 17 through Monday, Feb. 16.