(Sorry, I can't quote using BBCode since it's been disabled, apparently.)
***Mona Miller said: "Also, Queens..."***
Yup. :) In Buenos Aires province, what seems to be a Southern Monarch egg could de also a Queen's, or even a Tropical Queen's (Danaus eresimus) egg. But over here monarchs are common in urban and suburban gardens, while Queens and Tropical Queens are rare. So an egg on a cultivated milkweed plant is more likely to be a monarch egg than anything else.
***Mona Miller said: "Monarch Butterflies: Miles to Go Before They Sleep (and Lay Eggs)"***
Great article, I'm bookmarking it! :)
It's true that the migration habits of Southern Monarchs are still a mystery. They do migrate, but (to my best knowledge; I haven't looked up the subject lately) nobody has published a paper showing their migration patterns yet.
This bit of the article that caught my attention, though...
"In North America, monarchs exploit approximately 120 species of Asclepias milkweeds as larval host plants, but in South America monarchs only have access to six or perhaps eight species of Asclepias."
I think in the Southern Cone of South America (that is, roughly from Bolivia to the southernmost tip of the continent) there are about ten species of Asclepias... but there's also the fact that Southern Monarch caterpillars do not feed just on those. They also eat other plants, like Oxypetalum sp., and possibly also Araujia sp.
And, according to the plant list at the Darwinion Institute website ( http://www2.darwin.edu.ar/Proyectos/Flo ... sp?Letra=O
), the Southern Cone alone has 78 Oxypetalum species. That would mean much more salad for monarch caterpillars. :)