Well, you just found him and placed him some place new, so he probably stressed and will more then likely not want to eat for the next day or two. I'm not sure exactly where you are located, but pretty much crickets would be a fine staple and you dust them with repti-calcium and/or a vitamin supplement every so often. Mealworms are far from soft bodied and make a horrible staple. The chitin in their shell makes it hard for the frog to digest. They are fine every once in awhile, but not as a staple. If you have difficultly in obtaining crickets then you could try wax worms, hornworms, butter worms, etc.