By Joe Sebastiani, Seasonal Program Team Leader
Until a few weeks ago, the only Giant Swallowtail butterflies I had ever seen were in Florida. Recently, I have had two of these southern butterflies whiz past me, and finally today, I found one at the Flint Woods Preserve that I was able to get photos of while it was feeding. What is so special about seeing this large butterfly in Delaware? They normally are found further south from here, and are considered a rare stray to our area. This year is different. People are reporting them from all over the mid-Atlantic and even up into New England. This is the largest species of swallowtail that can be found in our area, and it is a beauty. It is dark on the back, with yellow lines that form an “X” near the wingtip. Underneath, they are largely yellow, with a blue median spot-band. The tails also have a dab of yellow in the middle.
Giant Swallowtail caterpillars usually feed on leaves of citrus plants down south, in fact, in some areas, they are considered a citrus “pest” species. Around here, there isn’t much citrus to go around, but some observers have seen them laying eggs on potted grapefruit and other potted citrus trees. Otherwise, the caterpillars have been known to feed on Prickly-ash shrubs. Too bad there isn’t any of that in Delaware either, at least not in the wild. It historically occurred here, but is thought to be extirpated. So what are these Giant Swallowtails doing here??? Who knows, but it could have to do with a super-abundance of them in one area, forcing them to leave to find new food resources, or it could have to do with weather patterns or other factors we haven’t considered. One thing is for sure, they are here, and you have a good chance of seeing them over the next few weeks.
There are other swallowtail butterflies in the area as well. Most commonly, you will see Eastern Tiger Swallowtails, which are large and very yellow. The black form of the Tiger Swallowtail doesn’t have much yellow on it at all. Black Swallowtails are smaller than Tigers and Giant Swallowtails. They are black and have yellow lines that do not cross. Other species include Spicebush and Pipevine Swallowtails, but they also have very little yellow. So if you see a big, black swallowtail, with yellow lines that cross near the wingtip, and a very yellow underside, it should be a Giant Swallowtail. Take a look around you flower garden, or go for a walk in a wildflower meadow and report back here if you find any. You can email photos to me at firstname.lastname@example.org if you want a species confirmation.