I start with a concept attainment lesson. I give the students examples and non examples of camouflage without telling them what they are looking for. I tell them yes if it shows camouflage and no if it does not. I tell them their job is to guess the rule I am thinking about.
Here is a portion of the slide show I use.
When the students figure it out we talk about what camouflage is and how it helps the animal.
We then each color a moth and hide it somewhere in the room. The object of the game is not actually to hide it, but to have it blend in to the surroundings. The students go searching for moths and try to find one. If they find one they stand in front of it until all the camouflaged moths are found.
Here are some examples of the students' moths.
I introduce the concept of mimicry by having them read an informational text article on mimicry. The students define these two words in their interactive notebook and we place a piece of newspaper down on the notebook. The students cut a moth shape out of newsprint and we place that on top. It really works and you can hardly see the moth!