Now for the background on my Photo of the Week, “When One Became Two.” A couple of decades ago, scientists noticed irregularities in Eastern Tiger Swallowtail butterflies, especially those flitting around the Appalachian Mountains. Their investigations showed that some of the swallowtails were bigger than others. Those that were larger were also paler in yellow pigment than the smaller ones. Enough evidence was presented that it was decided that the giant-sized swallowtail was actually a new species. Thus, the Appalachian Tiger Swallowtail was born. And yes, I realized I am oversimplifying the process and intense research.
I was ignorant of all of this information until I came upon the two different swallowtails side by side, feasting on the same thistle blooms. My wife and I were showing friends from Ontario, Canada, around Rockingham County, Virginia, recently when we saw the two butterflies. Even from our vehicle 30 feet away, we could distinguish that there was a significant size difference between the two tiger swallowtails. We also noticed that the larger one was not as yellow as the smaller one.
The journalist in me went to work after we bid our friends farewell. I was fortunate enough to capture the two butterflies in the same digital frame, which made it easier to compare their sizes and colors. As you can see, the Appalachian Tiger Swallowtail is indeed larger and paler than the more common Eastern Tiger Swallowtail. A check of multiple sources verified my conclusions based on these two main distinctions. Also, the only alteration that I made to the photo was to add my watermark.
So a few years ago the Appalachian Tiger Swallowtail butterfly was designated as a different species than the Eastern Tiger Swallowtail. My Photo of the Week, “When One Becomes Two,” shows why.
© Bruce Stambaugh 2019