I know this thread is pretty old, but just in case anybody is searching for info on Giant Mealworms...
I ordered my giant mealworms (Tenebrio molitor) from RainbowMealWorms.net
When I learned they might be sterile and that nobody seemed to know for sure, I contacted them. Our correspondence is below. Hopefully this will help somebody.
me: Hi,I ordered some of your Giant Mealworms without knowing enough about them apparently.Giant Mealworms are treated with a growth inhibitor hormone? is that correct?And if they do make it to beetle stage, are they sterile?Thank you for any info you can provide,RainbowMealWorms: Hi!Our regular mealworms and giant mealworms only differ in size. Our regular mealworms are available in sizes from 1/4" (mini) to 1" (large) and will undergo pupation to become a grain beetle.Our Giant mealworms have been forced to remain a larvae instead of pupating. The energy that they harness as larvae for turning into a pupae is instead channeled into making them grow 50% larger in width and length to 1.5" long. It is a myth that we give them a strange hormone to make them grow bigger; they only have the exact same hormones that any young unpupated mealworm larvae has.Thank you for your question, we are very happy to help in any way we can, and thank you so much for your order!Sincerely,
Me: ok. that's what I thought you'd say. Thank you so much for all the info.