Eastern Tiger Swallowtail: Bilateral Gynandromorph

Subject: Butterfly question
Location: Morganton, NC
September 14, 2013 12:37 pm
I took a picture of a butterfly over the labor day weekend in Morganton, NC. The butterfly has 2 different wings, one is black, the other is yellow. I posted the picture on a Facebook photography page. Someone replied that it was a tiger swallowtail hermaphrodite, bilateral gynandromorph.
I would love to learn more information about the butterfly. If you have any information, I would greatly appreciate it. I can email you a picture of the butterfly or you can view it on my Facebook page.
Waiting to hear from you. Thanks, Sandy Sisk
Signature: Sandy Sisk

Tiger Swallowtail:  Gynandromorph or not???
Eastern Tiger Swallowtail: Bilateral Gynandromorph

Hi Sandy,
Thank you for sending us your wonderful photo of a very asymmetrical Eastern Tiger Swallowtail,
Papilio glaucus, but we are not fully convinced it is a true gynandromorph like this example of a Tiger Swallowtail gynandromorph we have in our archives.  Male and female Tiger Swallowtails can be distinguished from one another by the blue markings on the lower wings of the females.  Your individual appears to us to be a dark female on the left and a light female on the right since there are blue markings on both hindwings.  See BugGuide for an explanation of the sexual dimorphism of Eastern Tiger Swallowtails.  Some female Tiger Swallowtails are transitional morphs, that are not light nor dark, but your individual is an unusual bilateral morph.  We are going to seek the opinion of lepidopterist Julian Donahue to see if he believes this is a gynandromorph.  More information on gynandromorphs can be found on the Dalton State website

Julian Donahue’s Assessment:  Bilateral Gynandromorph
It’s almost a perfect bilateral gynandromorph. But because of the unusual markings on the UPH on the right side, it may perhaps more properly be called an intersex, or a color mosaic. While bilateral gynandromorphs are most striking, all sorts of confused mosaic patterns have been documented.
I’m attaching a PDF of an article on this very subject, with color photographs of many examples, by Mr. Tiger Swallowtail himself, Dr. J. Mark Scriber. You can also link to the PDF at:

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