I used to feed my frogs ants but now they're too big. The trick I used was to lift up a big slab of concrete and there was an ants nest so I watched it until I saw where they were coming out. Once this is located I would get a piece of hay and a jar. Start poking the entrance with the hay a few times then leave it in the hole sticking out. This would aggrivate the ants so they would come pouring out climbing on the hay. Lift up the hay put it over the jar and brush them into the jar. When you continue you have to constantly slam the jar on the floor so they don't climb up the sides or you can put the lid on the jar.
Hope this helps.