Ewwww! What's in the 4th picture?
It looks like you have a good start on learning the camera since the pictures came out really good. I especially like the one by the water and the butterfly, although the rest came out good as well. The tooth picture made me shudder.

Those are cicada skins. Every summer they come up out of the ground and shed their skin. Then they fly up into the tree and buzz all summer long. They can be incredibly noisy.
Thanks everyone for the encouragement. Hopefully I'll be out taking some excursion pics.