For pet amphibians (amphibians bought at the pet store), I would say crickets are the best choice. Mealworms are ok, but too much of this insect can cause problems. I don’t like wax worms or earthworms because they always give my frogs diaherria when I feed them these, including my Whites tree frog. For wild (captive) amphibians, I would say spiders, moths, daddy long-legs, grasshoppers, beetles, and lace wings are excellent in addition to crickets. However, if you do harvest insects—as I do in the summer for my Wood frogs— make sure that no pesticides or other harmful substances are sprayed in your area.