Sunday, September 12, 2010

The Buckeyes are Leaving

The buckeye butterfly, Junonia coenia

Buckeye butterflies are passing through New York, heading south. I keep seeing them in the open sunny places that they like -- lawns and parks, roadsides, empty lots, and fields of weeds.

They are heading to the warmer places where they live year round like the southern United States, Mexico, and the Caribbean. Every spring some of them return to repopulate the northern United States and parts of Canada. Their southbound autumn flight is particularly noticeable along the coasts where at times they seem to be everywhere.

Adult buckeyes are about two and a half inches across. They are brown and tan, with a pair of orange bars on each forewing, and a series of large “eyespots” that may scare off predators when the wings open suddenly to reveal them.  (Oh no! Says the attacking bird -- some giant thing is looking right at me!) The caterpillars vary from dark greenish to gray or black with orange and yellow lines and rows of fancy spikes.

The buckeye caterpillar -- slim and stylish. 
 The butterflies sip nectar from asters, chicory and peppermint flowers, and some others. The caterpillars are especially fond of the foliage of plantains, snapdragons and toadflax.

Most of us are familiar with sexually dimorphic species, like lions or cardinals, where males and females look different. But buckeye butterflies appear in different forms in different seasons. The buckeye’s wings are tan underneath in spring, but red underneath in autumn; the change is probably linked to lower temperatures and shorter days. The difference is so pronounced that scientists call the forms by different names -- linea for the tan one and rosa for the other. 

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