One of the coolest things about female Eastern Tiger Swallowtail butterflies (Papilio glaucus) is that they come in two distinctly different colors, black and yellow. According to Wikipedia, that characteristic makes them dimorphic. I’m no scientist, so I had to do some research to see what “dimorphic” means. If I understand it right, it means that there are two different phenotypes (called morphs) that exist in the same population of a species and they have to be in the same habitat at the same time to qualify.
I was thrilled yesterday to observe and photograph both variants at a local garden. The yellow ones resemble the male, although the male is only yellow and black and has no additional orange and blue markings. I have seen a lot of the yellow female swallowtails this summer. The black swallowtails, which have black bodies as well as black wings, seem to be more rare, or at least I have seen them only rarely this summer.
Which one is more beautiful? I’ll leave that call to each of you.
Female Eastern Tiger Swallowtail butterfly (black variant) UPDATE in 2020: I think that I misidentified this as an Eastern Tiger Swallowtail and now think it might be a Black Swallowtail, though the angle keeps me from being sure about the identification
© Michael Q. Powell. All rights reserved.
Mike Powell 