My kids found this lying on our flagstones early this summer. It is large (more than 2 inches across), very light, somewhat furry, and beautifully marked. Interesting enough to spark some family curiosity. We dug around a bit on the internet, and discovered that it was the hindwing of a Polyphemus moth.

And some related interesting facts:
silk moth decline?
why eyespots?

I also found out that any caterpillars feeding on tree leaves (i.e. many butterfly and moth caterpillars like that of the Polyphemus) are killed when the “organic” pesticide Btk is sprayed to control gypsy moths. Gypsy moth is an invasive species from Britain that was introduced with the intent to develop an American silkworm industry. Now it is a big nuisance, periodically causing mass defoliation of eastern forests. Next year is apparently going to be a big year for damage in eastern PA

Here is a nice animation of the spread of the gypsy moth west and south from Massachusetts in the 20th century.