Harry LeGrand posted on carolinaleps this week a timely guide to differentiating Appalachian from Eastern Tiger Swallowtails, spurred by a great photo of the two puddling together. Here is Harry’s post with the submitted photos:
“Brian Bockhahn allowed Tom Howard to upload his two photos of a puddling Appalachian Tiger Swallowtail (*Papilio appalachiensis*) with a puddling Eastern Tiger Swallowtail (*Papilio glaucus*). You can easily tell the difference on these two; the most obvious mark is the large size of Appy, which can dwarf an Eastern.
1. Appy ground color, especially above, tends to be a pale yellow, often
noticeably lighter than the medium yellow of Eastern. In many cases, there
is less black and more yellow on Appy, as compared with Eastern (visible
2, The HW of Appy is very long and “stretched”-looking. with a mainly
straight outer edge. Eastern HW is shorter and somewhat slightly convex
(curved). As a result, the yellow on the HW in Appy is somewhat more
V-shaped toward the tail; Eastern yellow is more rounded or U-shaped toward
3. The outer edge of the yellow ground color on both wings of Appy, as seen
from above, tends to lie in a straight line from FW tip to the HW area near
the tail. On Eastern, when you follow the yellow outer edge from the FW
down to the HW, the yellow on the HW is offset and curved outward, and thus
is not a straight line.
4. On the FW, from below, the marginal yellow band of Appy tends to be a
narrow band, and not clearly broken into spots. In Eastern, this marginal
row is clearly composed of rounded yellow spots.”
See the full species account here.