Had 2 black dots on it's back too.. I tried to get good pics of it but couldn't, it was moving around too much.
This is the best I managed, mostly hoping just the colors will give it away.
A tad out of focus to determine what it is.
If just one, probably not a problem. If more, perhaps it's wise to get an ID.
You should be able to get info from your county's Extension Service office. Find your office w/ this map.
Here is a link that might be useful: locate your county's Extension Service office