In anticipation of the first swallowtails of the season in the South, Harry LeGrand shared a picture (from Doug Allen, on the NABA sightings page) and ID tips on distinguishing Appalachian Tiger Swallowtails from Eastern Tigers. This will come in handy for a LepTrek we hope to schedule specifically for Appy’s this spring at WABC.
This photo (and several others linked to in Harry’s post) gives a great comparison of the much smaller Eastern with the large, pale yellow Appalachian. Harry points out some of the diagnostic marks one can easily see from this photo and offers additional info on the NABA-chat listserv:
1. Appy is MUCH larger than Eastern (in their first brood); Appy apparently has no second brood.
2. On Appy, there seems to be a smaller percentage of the wings covered by the black stripes, maybe because of the larger size, but that is one thing one notices about Appy — a lot of yellow compared to black, whereas on Eastern, it seems to be a relatively higher % of the wing covered by the black stripes.
3. Appy is paler yellow, on average, than Eastern. That may not be overly obvious in this photo, and many first brood Easterns can be pale yellow. But, the key is that Appy is ALMOST ALWAYS this pale, creamy yellow. Easterns are often a medium yellow, to even a richer buttercup yellow. Any Tiger that is a medium yellow is essentially not an Appalachian.
4. When the butterflies are spread open-winged, from above, the separation line of yellow and black — i.e., the wide black margin — on Appy is essentially straight from the FW down through the HW, all the way to the tail. So, from the tip of the FW to the tail, the black-yellow margin is STRAIGHT. In Eastern, this separation line is usually broken from the FW to the HW, such that on the HW, the separation goes OUTWARD. So, from the FW tip to the tail, the yellow-black border is not straight. This is very easily seen in the Eastern on the right. You can not draw a straight line from the FW tip down to the blue spots on the tail.
Several other field marks from above aren’t quite as obvious because of the poor angle of the Eastern in the photo.
5. The HW of Appy is quite long and “drawn out”, compared with the typical Eastern. This leads to:
5a. The HW outer edge of Appy is rather straight, from the leading margin to the long tail, and this margin is more rounded in Eastern.
5b. The yellow ground color of the HW of Appy is usually a “V” shape, such that the lower margin is pointed at the tail. In Eastern, the yellow color on the HW is “U” shaped, with a clearly rounded black-yellow margin near the tail. Again, you can see this a bit, in that on Eastern, the shorter and more rounded tail has the more rounded black border on the HW, whereas on Appy the black border is rather straight.
There are several marks from below, mainly:
6. Appy has a very wide and noticeable silvery-blue-gray submarginal band (about as wide as a pencil or pen); in Eastern, this is much narrower and does not catch the eye.
7. The yellow marginal FW spots TEND to be more rectangular and form a band in Appy, and more rounded or spot-like in Eastern, not forming a band. This can be tricky. See underside photos of both at:
(Will Cook provides excellent comments with his photos on his website!)
Appalachian Tiger Swallowtail is a common to very common butterfly species in the southern Appalachians from April into May, and often into June or early July (high elevations then), and they often outnumber Easterns. They ARE SYMPATRIC with Easterns, flying together at the same time, place, elevation, etc. — as can be seen by both species at the same puddle or dirt patch.
So, when you are butterflying this spring and summer in the central and southern Appalachians, be prepared to study both species, especially when the males are on the ground at puddles or dirt. (I note that when Doug Allen took his SC photo, his tally was 22 Appys and 4 Easterns).
Harry LeGrand, Vertebrate Zoologist
North Carolina Natural Heritage Program
NCDENR Office of Conservation, Planning, & Community Affairs
1601 Mail Service Center
Raleigh, NC 27699-1601
Office: (919) 715-8697