The Viceroy Butterfly is often confused with the Monarch. As you can see the colors are the same and the size appears to be nearly identical.
The main difference is...
If you look closely there is a narrow black curved bar across the middle of the (back) dorsal hind-wing. This is the tell-tale sign that is a Viceroy and not a Monarch. The Viceroy is also a bit smaller than the monarch.
It is found in all regions of the state has a flight period of June, July, and August.
It likes wetlands and openings in woods.
It is always found close to willow and poplar trees. These trees are the host plants for the Viceroy larvae.
The Monarch butterfly leaves a bad taste in the mouth of predators that try to eat it. Since the Viceroy looks much like the Monarch, predators likely avoid it for the same reason. It has also recently been determined that the Viceroy has a bad taste of it's own.
So, over time the Viceroy evolved to look much like a monarch. They did this to avoid being eaten.