Gotta find them all!

The park across the street has a sign advertising some of the organisms that are likely to be found by visitors to the park. (Note that the sign does not include the organisms most likely to find visitors to the park, namely the mosquitoes and chiggers).

Which one of these doesn't quite belong?

I have already made considerable progress in documenting each of the organisms on the sign (and have either seen or heard all but one of them).  Here is a quick guide to each organism, starting from the top left of the sign:

Ladybug: I have found at least three species of ladybugs (a.k.a. lady beetles) in the park.  However, since the drawing was specifically of a seven-spotted lady beetle, I will show that species too.  This species was an interesting choice for the sign, given that it is not native to North America.

Two seven-spotted lady beetles (Coccinella septempunctata).

Dragonfly: I was absorbed in watching a bee (notably omitted from the sign) when I was startled by the sound of the dragonflies pictured below.  They were making a violent clattering as they beat their wings against the vegetation in their struggle.

A male (left) attempting to mate with a female (right) variegated meadowhawk (Sympetrum corruptum).

Turtle: I didn't even have to cross the street to find a turtle.  The one pictured below was on the grass along the sidewalk outside my apartment.

Probably a red-eared slider (Trachemys scripta elegans), but it was hiding its "ears" along with much of the rest of its head.

Squirrel: You may have noticed that I skipped over the acorn.  I don't remember seeing any in the park, but they may have been there (I was not looking specifically for them) or they may have all been hidden by the many squirrels, most of which appear quite well fed.

A fox squirrel (Sciurus niger), but still no acorn.

To be continued...