I have to go with the myth. I raised chameleons for years and they had a steady diet of mealworms and I mean steady. That was the majority of their diet. I also raised exotic finches for several years and fed them mealworms as a treat, again no problems. I had heard that the super mealworm was the cause of this rumor but it had never been proven. As for chickens, there is not much they don't eat as long as it doesn't eat them first.
Ken
Ken