Milkweed

Did you know that... Sap from milkweed was used by pioneers as a cure for warts? The airborne fluffy parachute of the seed was used by Native Americans to insulate moccasins? The dried empty seed pods were used as Christmas tree decorations by early pioneers? The boys and girls from Wisconsin schools collected 283,000 bags of milkweed fluff for use in military life jackets during World War II? It is used as an indicator of ground-level ozone air pollution? Find out how to conduct a milkweed check-up to check for signs of pollution. (facts courtesy of Wisconsin Dept of Natural Resources)

Milkweed Bugs:
In the photo above you can see the orange milkweed bugs.
These orange and black bugs concentrate bad tasting compounds found in the sap of the milkweed plant.
Their bright orange color is for advertising their bad taste.  Inexperienced birds that taste their first milkweed bug won't be eating another orange and black insect any time soon.  There are other orange and black bugs that aren't bad tasting, but don't get eaten, just because they mimic the milkweed bug. 
Milkweed bugs are one of a small group of insects that have the ability to tolerate the toxic compounds in the milkweed plant. They are therefore important in regulating populations of this plant.

Monarch Butterfly:
The monarch butterfly is sometimes called the "milkweed butterfly" because its larvae eat the plant. In fact, milkweed is the only thing the larvae can eat! If you'd like to attract monarchs to your garden, you can try planting milkweed (if you live in the right area).
Adult female monarchs lay their eggs on the underside of milkweed leaves. These eggs hatch, depending on temperature, in three to twelve days.

Most predators have learned that the monarch butterfly makes a poisonous snack.  The toxins from the monarch's milkweed diet have given the butterfly this defense.  In either the caterpillar or butterfly stage the monarch needs no camouflage because it takes in toxins from the milkweed and is poisonous to predators.

This is a photo of a Viceroy:

The Viceroy is not a poisonous snack for a predator, 

but has evolved to look like the monarch so he won't get eaten either.

This is the Monarch:

The way to tell them apart is the Viceroy has a black stripe along the bottom if it's wings.