Papilio machaon oregonius breed twice a year, and can be seen on wing from April to September.
   The butterflies seen toward the beginning of the year are lighter in color than those seen later and blend well with the color of early plants.
   They are strong, wary fliers that are very difficult to capture.
   Their preferred terrain is below 4,000 ' in elevation, in sagebrush dominated canyons, plateaus and mountains throughout the Columbia and Snake River basins.
   Adults are also known to often hilltop.
   The adult has a yellow abdomen with black lines.     Its wings have concave spots that are scalloped inwards with a reddish orange eyespot along the lower border, similar to, but smaller than the eyespot of the common Old World swallowtail.
   The yellow markings on the wings of the Oregon swallowtail are also brighter than the common swallowtail. They have a tail characteristic of all swallowtail butterflies.
   The caterpillar is black with yellow markings.
   *  In 1976, they became one of the first four butterflies that the United States Postal Service placed on a U.S. stamp.
   * * The Oregon swallowtail was declared the state insect of Oregon in 1979 by the Legislative Assembly.