How did you get them? Did you collect them?Relatively easy to get a few, but it can take a couple of months to bring them up to an appreciable amount. I had a 'bug box' of dermestids used for skeltonisation a few years ago, but they were a pain to maintain when not being used.
Ward will clean out your bank account, go to taxidermy.net and you should be able to grab them up by the thousands cheaper than crickets.Here you go, a source used by hobbyists, scientists, and teachers.
Speaking of crickets, I have seen Dermestid larvae in cricket boxes before. YOu can always ask to comb the cricket bin at your local pet store.Ward will clean out your bank account, go to taxidermy.net and you should be able to grab them up by the thousands cheaper than crickets.