In late summer an influx of southern butterflies and dragonflies move into western Pennsylvania.  These are insects that are ill-equipped to survive northern winters, yet they expand their range northward.  These emigrations are difficult to predict.  They vary in distance and numbers each year.  In some species there may be no movement at all one year, then huge numbers are on the wing the following year.

    This gallery portrays the butterflies, and one of the dragonflies, that may move north.