Butterfly - not as funky as the other one

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salden
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Butterfly - not as funky as the other one

Post by salden »

Anyone have an ID? I think it is a type of swallowtail. Location: Pennsylvania

Image
Sue Alden

rjlittlefield
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Post by rjlittlefield »

Sue,

It's a "Red-spotted Purple", Basilarchia astyanax, or Limenitis arthemis astyanax, or Limenitis astyanax, depending on who you listen to.

Warning: arguably excessive technical detail follows! :wink:

In "How to Know the Butterflies, Paul Ehrlich 1961, astyanax was considered to be a distinct species, although Ehrlich also wrote that
This species is considered by some to be conspecific with the more northern L. arthemis, with which it hybridizes in a narrow zone in southern New England, New York, northern New Jersey, Pennsylvania, Michigan and Wisconsin. The continued distinctness of the parental types in the area of overlap, however, suggests that they are best considered distinct species.

The National Audubon Society Field Guide to North American Butterflies, 1981, refers to the whole genus as Basilarchia, not Limenitis, but continues to represent the relationship with arthemis as hybridization between distinct species. BugGuide.net, on the other hand, and other modern publications, have it as a subspecies of L. arthemis.

Whatever one calls the beasts, it seems clear that there's a northern population (arthemis) that looks and acts one way, a southern population (astyanax) that looks and acts another way, and a fairly narrow geographic area where those two forms come together and interbreed freely with no significant penalty to the hybrids. What causes this unusual situation is still under investigation. In a quick Google search just now, I found an abstract as recent as March 2006 addressing this question.

These butterflies occupy a special place in my heart. Back in 1973, when I was taking a college course in Evolutionary Mechanisms, I noticed that our textbook had what seemed to be a rather shaky use of the arthemis-astyanax complex to justify the author's claim that disruptive selection could not cause speciation. Investigating the literature yielded a rather nice class report, since it turned out that within the complex, at least according to data published by that time, there simply was no disruptive selection! I have no idea how the textbook got written as it did, but as an undergraduate student it was notably pleasant to essentially say "Poppycock!" to a chunk of textbook, and get a good grade as a result!

Very nice picture, by the way! :D

--Rik

salden
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Post by salden »

Thanks Rik,

This is my favorite BF that is in my garden. I could not find a "positive" id for this particular BF, but plenty of "similarities" in my book and I did look on bug guide, but again, nothing exactly what I had.
Sue Alden

Ken Ramos
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Post by Ken Ramos »

Nice BF Sue. I got a photo of one of these too. Found it in the field out behind the plant at work. :D

beetleman
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Post by beetleman »

A beautiful picture Sue. I like the way it is composed...very nice.
Take Nothing but Pictures--Leave Nothing but Footprints.
Doug Breda

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