I am betting this has been asked a billion times but when I looked it up on Google everyone had a different answer. a few weeks ago I 1000 small Dubia roaches and noticed there was a black beetle in with them, figured it was a trash eater. Now I have dozens and dozens of little black worms. As I said I researched them on Google and got answers from they will destroy your colony to they are cleaners themselves and won't hurt the roaches. Here is a picture, please let me know if my colonies are safe or not. I have found them in my large roach colony too but not my adults.
Hi there....those are dermestid beetle + larvae. I can't say if there's any danger to dubias since I never used them but they never harmed the 1000's X 1000's of crickets I used to get in bulk.