Tuesday, June 30, 2009

Two Ladies

The American Lady and Painted Lady butterflies are both found in Caddo Parish. It seems they are usually found at different times - American Lady in the spring and summer - Painted Lady in the fall. We still have to be able to tell them apart, and here's how:

"American Ladies have big eyes!"

Looking at the ventral sides, you can see that American Lady butterflies have two large eye spots, whereas Painted Lady butterflies have four smaller eye spots.
If you miss the botttom view somehow and only get a glimpse of the dorsal side, American Lady butterflies have two blue spots flanking two dark spots on each hindwing. Painted Lady butterflies have four dark spots with no blue.
There are eleven more days until the Ninth Annual Shreveport Butterfly Count. I will try to distinguish between as many of the tricky ones as I can between now and then...

Black Swallowtail Clarification

It is worth noting that the field guides I read suggest altogether different field marks for the Black Swallowtail. Also, my pupil-in-the-iris shortcut only works because here in Louisiana we do not have the other western swallowtails with that same marking.

Many people who know more about butterflies than me (as there are many many people who know more about butterflies than me), point to the parentheses-shaped markings and the second row of spots as diagnostic.

These field marks are helpful when they are all there, but sometimes they aren't.

Moreover, sometimes, the Eastern Tiger Swallowtail dark morph has markings that could be mistaken for Black Swallowtail parentheses.
As for the pupil-in-the-iris, it is also found on the Anise Swallowtail, Indra Swallowtail, and Old World Swallowtail. The Old World Swallowtail has a subspecies called Baird's that looks remarkably similar to a Black Swallowtail. These species are western and are not found in Louisiana.
There is a section of the U.S. where their ranges overlap with the Black Swallowtail. If you live within the red rectangle, then you certainly cannot count on the pupil-in-the-iris to be diagnostic.

Tuesday, June 23, 2009

Four Dark Swallowtails

According to Butterflies and Moths of North America, there are 926 species of butterflies known to live on the continent. Jeff Trahan – with help from Rosemary Seidler, Terry Davis, and me – has found 97 of them in Caddo Parish.

So far.

Four of those species are commonly called “the dark swallowtails,” and those four species can be tricky to tell apart. They are the Pipevine Swallowtail, Black Swallowtail, Spicebush Swallowtail, and the dark morph female Eastern Tiger Swallowtail.

To distinguish between them, let’s look at them at the same time.

Dorsal View
Ventral View

Okay, look at them again. This time, focus on the field marks, or things that define each species.

Dorsal View
The top left is a Black Swallowtail. Males are unmistakable because instead of white spots, they have yellow spots, and they have an extra row of them. The female is pictured here. Male and female Black Swallowtails can always be identified by the black dot inside the orange dot. There are also some differences in the size and shape of the white spots on the forewing, and some other distinctions, but "pupil-in-the-iris" orange/black spot is a dead giveaway.

The top right is the female Eastern Tiger Swallowtail, dark morph. Notice the white spots on her forewings are really dashes. Also notice the white spots on her hindwings have a little orange in them, especially the ones on either end of the row. Sometimes you can still see a little yellow and maybe even a tiger stripe, but the dashes and the extra orange is always there. She's a bit bigger than the other dark swallowtails, too.

The bottom left is a Spicebush Swallowtail. There are some differences between males and females, but both sexes always have those fingertip-shaped spots on the hindwing that are bluish-white.

The bottom right is a Pipevine Swallowtail. There are subtle differences between male and female Pipevine Swallowtails as well, but both sexes have blue tails. Also, the blue color on Pipevines does not seem to be compartmentalized the way it is on other dark swallowtails, but rather blended looking.

Ventral View

The pupil-in-the-iris is still visible when viewing the ventral side of the Black Swallowtail. There are pretty much two rows of orange spots, and the row closest to the body has a double spot.

"Tigers do not have spots!" At least female Eastern Tiger Swallowtails do not have spots on their bodies. All the other dark swallowtails do. Also, the dashes are still visible.

Often you can see some of the dorsal side when Spicebush Swallowtails' wings are closed, and when that happens, you can still see those bluish-white fingertips. With only the ventral side of the hindwing showing, you can see that Spicebush Swallowtails have two rows of orange spots, minus one. That absent orange spot is diagnostic.

Sometimes you can still see the blue of the Pipevine Swallowtail's tail on the ventral side. Sometimes you can tell that the body is a bit blue (the others are pretty much black). Regardless of whether you can see that blue or not, you can always identify a Pipevine Swallowtail with its wings closed by counting the rows of orange spots. There's only one row.

To test out these identification short cuts, grab your binoculars and head out to the park for some butterfly watching. Swallowtails fly fast and high, so you may have to let some go uncounted.

But it's the thrill of the hunt, right?