Yes some will readily take fruit flies, the flies tend to form small floating groups and then the newts come and grab them like some giant shark eating seabirds from the water surface. Fewer flies escape then you would think.
If you've got a couple of floating plants (especially Pistia sp.) some newts will hang on to them to stay close to the surface as the flies use the plants to walk on. When I've caught a annoying house fly or mosquito I feed it to my newts larvae using tweezers.
My axie is acting woerd he was a rescue as stated in a different post he got better and now seems to be deteriorating again...again all tank conditions are OK and as should be. He seems to have some black dapple like pattern under his bottom lip? Is that normal? And his two back feet have a little wierd growth? Almost? Tiny tiny tiny lump. His capillaries in his feathers also appear darker and more visible. Any help would be appreciated