Erin Krichilsky is a research assistant at the Smithsonian Tropical Research Institute (STRI) in Panama. In 2018 she examined a unique sweat bee that appeared to be male on one side, and female on the other side -divided exactly in half like a side show performer, but without the costume. This was a gynandromorph, which is so rare that this is only the second gynandromorph bee found in 20 years.
In humans, biological sex is determined by two sex chromosomes—one from mom and one from dad. Inheriting two X’s yields a female, while an X paired with a Y creates a male. But bees do things a little differently. All fertilized eggs, which carry genetic material from a mother and a father, hatch female bees. Unfertilized eggs, however, can still yield offspring: fatherless males that carry only one set of chromosomes from their mothers—half of what’s found in females. Sex, in other words, is determined by the quantity of genetic information in a bee’s cells.
That's very weird in itself, but bees might consider the way humans do it to be very weird. Scientists have a couple of different theories as to the genetic mishap that caused the gynandromorph bee. They also did a behavioral study of Krichilsky's bee, still alive when it was discovered, which you can read about at Smithsonian.
(Image credit: Chelsey Ritner/Utah State University)