Yes, mites will infest your Drosophila stocks if you don't use clean techniques
and/or you don't flip your vials very often. They're very small, but you can
see them with the naked eye (barely). They will definitely suppress the growth
of your fly stock. Best way to avoid mites is to change your vials often (no
longer than once per generation) and to avoid exposing your cotton plugs (or
whatever top you use) to any dirty environment. There is also insecticidal
paper that you can put beneath your stock trays to prevent mites from growing
outside your vials.
> Has anyone heard of "drosophila mites?" Supposedly they are pinkish in
> colour and hamper the mating of drosophilas. If anyone knows anything about
> these mites or any other mites that infest drosophila cultures please let me
> know. Thanks.