Are they young yet? If so, I would feed them as many as they're interested in eating. If they're older, I'm not sure. I don't have much experience with bumblebees. They won't "pop" but you may want to watch if they end up getting overweight and then cut back. I never limit my red eyes' food, but my greys will eat themselves obese...so it really depends on the frog/toad. Hopefully someone with experience with them pops in soon and lets you know