The Pine Woods Treefrog like several species of frog has bright colors on
concealed part or the leg. These brightly colored areas are "flashed" in an
attempt to startle potential predators. On the Pines Woods Treefrog the
bright colors are on the inner thigh. This characteristic is included as
part of the scientific name:

Hyla - is Greek and means "belonging to the woods".
femuralis - is Latin meaning "pertaining to the hind leg", referring to the
leg markings.