Are maggots bitter?

I bought some undyed maggots from a local gas station bait section (only place to find any here) and changed the wood shavings they were in for wheat bran mixed with fish flake food (to reduce smell and feed them) before storing in my fridge.

I've been feeding them to small frogs. I've noticed that they'll eat them, but they act like they taste gross. They do a funny backwards dance, and like rub their faces on the Eco Earth. It's not the same face they make when eating the Hydei flies I've started culturing. (A blinking gulp.) The maggots were meant to be an in-between food while the fruit flies are getting established, but they're definitely less work.

I've bought Nightcrawlers from there repeatedly for my salamander and haven't had any issues (I wait 24 hours for them to clean out first in fresh dirt.)

Are maggots just nasty tasting or is something else going on? The frogs seem fine health wise.