Until recent years, this butterfly could be
seen in large numbers in late July and August flying high near the tops of pine
and fir trees, but it has been increasingly scarce since the mid 1990s. The
flight is characteristically light and floating, reminding one of a small fragment
of tissue paper floating in the wind. Winter is spent in the egg. The caterpillars
feed high, near the tops of pine or fir trees, and it is usually necessary to
climb a tree to find them. They pupate also among the needles, high up. Caterpillars
found on the ground are probably parasitized. The adults are sexually dimorphic.
The one shown here on a thistle flower is a male; the other is a female.