Monarchs remain a common sight throughout the U.S. and Canada due to the continued abundance of the milkweed, the only
food monarch caterpillars eat.
This may seem like a restricted diet, but there are over a hundred
species of milkweed in North America.
Milkweed is notorious for its digitalis-like toxin
that is harmful to many animals, including humans. As caterpillars,
monarchs ingest these poisons, store them in their own tissues, and
retain them through their metamorphosis as an adult.
Essentially, the monarchs are taking the plant's protection
and using it as their own against predators, such as birds.
A bird that eats a monarch will not die, but it will become quite
ill. As a result, birds learn to avoid anything colored
orange and black.
Other non-poisonous insects have adapted the same coloration
since, in the animal world, orange and black acts as a universal "Toxic:
Do Not Eat" warning.
Monarchs originally were a tropical species which gradually
moved north after the last ice age to take advantage of an increased
food supply in the United States.
But after spending summer in the States,
the animals depart until their staple food, milkweed, is available again
the following spring.
Butterfly Life Cycle
Where To See
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