Pacific Grove and the Monterey Peninsula hosts the best known butterfly noted for its migratory journeys the Monarch Butterfly. Primarily a tropical butterfly the Monarch species is part of the brush-footed butterflies, whose main characteristic is the tiny forelegs that are useless for walking.

Monarch Butterfly larva feed exclusively on milkweed plants a fairly abundant food source in its habitat range. The milkweed plant is a weed found all along road sides and many rural areas.
The milkweed plants imparts a poisonous latex like sap. Monarch larva eat the leaves of the milkweed and store the poison in their bodies to repel birds and other predators.

A Monarch impostor the Viceroy Butterfly takes advantage of the Monarchs poisonous reputation by mimicking the Monarchs size and coloring. Viceroy Butterflies live primarily in the eastern United States.

Monarchs typically migrate 2,000 miles from Canada and Mexico and back again. The butterflies lay eggs along the migration route, many generations are laid in one year. The cycle change from egg to butterfly takes about 4 weeks. Monarchs are 31/2-4" (88-100 mm) in size. In Canada the Monarch butterfly is called "King Billy" in honor of King William of Orange whose colors were orange and black.