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Eastern Black Swallowtail egg? - Limenitis arthemis

Eastern Black Swallowtail egg? - Limenitis arthemis
Chesterfield, St Louis County, Missouri, USA
September 22, 2013
Saw butterfly laying egg

Images of this individual: tag all
Eastern Black Swallowtail egg? - Limenitis arthemis Eastern Black Swallowtail egg? - Limenitis arthemis

Moved from ID Request.

Interesting, all of the Easte
Interesting, all of the Eastern Black Swallowtail eggs I have seen are quite smooth. Also can't figure out what it is sitting on. Perhaps a form of Limenitis arthemis just a wild guess -Red-spotted Purple?

Too accurate to be a guess.
It seems your initial guess was spot on. Speaking of accuracy, how was the Red-spotted Purple able to find that one spent egg on which to deposit a new egg. There are several Quince bushes in my yard. They are fairly far apart. The Red-spotted Purple flew in, landed to check a few nearby leaves, laid the egg exactly on a spent egg and left. I found no other eggs in that vicinity..

Swallowtail eggs are smooth and spherical; this looks exactly like a Limenitis egg, and quince is a reasonable host for red-spotted purple (which could easily be mistaken for a black swallowtail).

It does seem like it was deposited on another collapsed/defective egg of the same species. I've never seen that before.

I agree...
It looks like the egg is sitting on a hollow shell or defective egg of the same kind.

The Carolina Nature page on the Red-spotted Purple Limenitis arthemis astyanax has a nice photo of an egg. I'd say it matches the ID request pic to a T.

I also note that (according to my field guide) black swallowtail host plants are usually in Apiaceae (Umbelliferae when I was younger) -- the carrot family, and sometimes Rutaceae, the citrus family.

But the quince is in Rosaceae -- the rose family.

Agreed. Thanks bunches
The pictures on the Carolina Nature site match what I saw. Those pictures were not in my Missouri guide to insects and spiders. The bluish color, spots, and egg on tip of leaf are a perfect match.

It is on the tip of a Quince
It is on the tip of a Quince leaf. The egg is quite small. I got a very murky picture of the butterfly and my memory is weak. The closest I could come to the species, based on blurry color patterns, and from my field guide the Eastern Black Swallowtail. However there was a dark bluish tint to the solid color.

Thanks - more description
The forward section of wings appeared to be solid. The back edge had two strings of light color spots. The rear most were small and the forward most spots were elongated. I don't remember much else. I was focused on her actions.

As someone who respects later
As someone who respects lateral thinking and has no particular ideas about what egg this is, I'll offer the idea that it looks like the fresh egg might be placed upon a collapsed earlier egg. How would that be advantageous, I wonder. Maybe chance?

However, that is a possibilit
However, that is a possibility. I could not see the detail with the naked eye - only with a super close-up.

I'm skeptical it's just glue;
I'm skeptical it's just glue; too much fine structure that seems to resemble the fine structure of the fresh egg. And just another lateral thought, the old egg might present a physical (all those spines) as well as possible chemical defense. Maybe also nutritional support?

Chemical defense or Nutritional structure?
Can or do butterflies lay a defense barrier on which to lay their egg.

I wasn't thinking of a defens
I wasn't thinking of a defensive barrier except in the abstract. My thought was that defensive chemicals either gathered or synthesized by the caterpillar, might be inside the egg (so no need for a specialized barrier). Also, the spines look defensive, though I do not know what they might defend against; maybe parasitoid wasps or predator ants?? And since caterpillars often eat their shed skins (exuviae), there might be a nutrient/defensive chemical-based value in laying an egg on an old egg. Depending on the cause of the old egg's demise, there might be who-knows-what chemical signal going out saying, perhaps, something advantageous to the new kid.

I posted a cropped image from the Raw file.
I don't know how to keep the two pictures under one comment stream, but take a look at the blow-up of the egg and let me know your thoughts.

Good observation. A glue woul
Good observation. A glue would most likely be solid. I thought the leaf color was showing thru the white structure under the egg, but it could part of a second egg structure.

I believe the white matter un
I believe the white matter under the egg is a form of glue. I watched her lay the egg.

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