Tree Frog Not Eating

[alex1976]

Okay, it's been about two weeks since I first put this little guy in the tank and he's yet to eat that I know of. He's wild caught and pretty small. I hand feed all my GTF's to insure they all eat. The others have all learned that fingers mean food and eagerly jump to my hand when they see it. He's yet to learn this and jumps away but will not take food even when it's moving in front of him. He doesn't look stressed (he's a very pretty green with a star pattern on his back). He looks a little thin but not terrible.
Is there anything I can do? Should I isolate him with crickets and see if he'll eat on his own? Should I attempt to force feed him??? I'd just hate to stress him out even more so I've just been dangling the food in front of him with the rest when I feed them but he just won't take it. I've tried small crickets and small moths. He did seem to get excited about an ant though when one was outside the tank but I didn't know if they were safe...
Are ants safe for them to eat??
As always, any help and ideas are always welcome.