Sunday, August 14, 2011

Another Dark Swallowtail

My son and I drove out to Union Lake, just west of the interstate, today to see what birds might be out and about. From there we went on through Lonsdale, about halfway to New Prague, and then circled up through Elko New Market and back via rural roads. We caught a great blue heron hanging out next to a lone white pelican (too far away to get a photo). We saw a double-crested cormorant and plenty of gulls and pigeons. We saw a large hawk on a line overhead, and lots and lots of tree swallows also on lines. A small number of killdeer, some Canada geese, and a few quick, darting songbirds here and there completed the picture.

Probably the most memorable spot of the day was not avian, but lepidopteral.I caught a glimpse of something black and ragged-looking fluttering among the roadside clovers and wildflowers and pulled over to take a closer look. I wasn't even quite sure whether it was a bird or a butterfly, it was so large, but it turned out to be a huge black butterfly with blue hind wings. The sun was shining on my LCD display so that I could hardly see whether I'd captured it in the photos or not, and as you'll see the focus isn't great.

As I first saw it - huge and very black. Those are large clover blossoms!
Here you can see the blue hindwings and a hint of the swallow-type tail
I was able to get quite close to take this photo
I thought this butterfly seemed much blacker and to have more blue on its tail than the female dark-form eastern tiger swallowtail (Papilio glaucus) I recently blogged about. The ragged-edged appearance of the wings from a distance proved to be due to the spots/checks that form the wing borders.

As I first researched other similar butterflies I thought it might be a spicebush swallowtail (Papilio troilus) because of that larger blue area. But as I looked at more and more sources, I came to the conclusion that this is indeed another of the same. Features that convinced me included the orange spots at the base of the hind wings and where the hind wing meets the fore wing on each side, and the yellowish color of the spots at the edge of the hind wings, compared to a cooler almost blue tone to those spots in the P. troilus. Of course, then I compared the range maps and saw that it was much less likely to have been the P. troilus, which doesn't seem to extend past Wisconsin into Minnesota. So there you have it.

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