The ones we used to have were good layers, were pretty to look at, but we could not let them free range. They would attack anything ducks, little dogs, and my husband!
I have done my own research with animals and DE, and I know that it is useful in treating mites, lice, and parasites. No scientific papers published, but 20 years of raising chickens using nothing else but DE. I dust them with DE, use DE in their food, sprinkle DE throughout the chicken house...