The Academy of Natural Sciences of Drexel University has over 3 million specimens in its entomology collection, but one butterfly stands out from the rest. The butterfly is literally one in a million because it exhibits both the physical characteristics of a male and a female.

Retired chemical engineer Chris Johnson from Swarthmore, Penn., was volunteering for the Academy's Butterflies! exhibit in October last year when he spotted an odd butterfly while emptying the exhibit”s pupa chamber. The pupa chamber is where cocoons and chyrsalises are placed.

Johnson related that, as the creature opened up, he noticed that it was different from other butterflies. Its two right wings were those typically found in the females of the species, which were brown and marked by white and yellow spots.

The insect's two left wings, however, were smaller and darker with green, purple and blue markings, which characterize males. The coloration of the body was also perfectly split lengthwise down, essentially making the butterfly half-male and half-female.

Entomology Collection Manager Jason Weintraub, a butterfly expert who was contacted to examine the bizarre-looking insect, confirmed that the butterfly was a Lexias pardalis, a member of the butterfly family commonly called "brush-footed" butterflies.
The lepidopterist, likewise, said that the butterfly had a rare condition known as bilateral gynandromorphy, which is characterized by having both the male and female external characteristics.

The condition is different from hermaphroditism. A hermaphrodite only has the outward characteristics of one gender but has both the reproductive organs of the male and female.

Weintraub said that the condition is most noticeable among birds and butterflies because the two genders of these species have distinctly different coloration, but scientists do not currently know how prevalent the condition is because it can easily go unnoticed in animals where the males and females resemble each other.

He explained that the condition may happen when an organism's sex chromosomes did not separate during cell division in its early development, which causes some of the cells to have a female genotype and the others to have a male genotype. This leads to the animal having the characteristics of both sexes.

"In most cases, such specimens are 'discovered' in museum collections by a researcher who is carefully examining reproductive organs of insects under the microscope and stumbles across a specimen with both male and female characteristics," Weintraub said.

The butterfly was among the pupae shipped from a butterfly farm in Malaysia's Penang Island in October. Lexias butterflies live in Southeast Asian rainforests.

The special butterfly, which has a short lifespan typical to its kind, has been preserved and pinned. It will be exhibited at the Academy from Jan. 17 to Feb. 16.