Drosophila  spp.
I know that many people have found the large, black species of Drosophila fickle to culture, and I think I may have discovered how to prevent this.  Like most people, I have had failures of these flies for no apparent reason.  Their life cycle is considerably longer than that of D. melanogaster, and the failed cultures usually  moulded up.  I have found that the problems can be alleviated by starting new cultures with masses of flies and by initially keeping them at about thirty degrees Celsius.  This way larvae appear after two or three days and the flies can then be used to start a new culture, or fed to the frogs.  The medium is the standard mashed fruit mixed with some thickening agent (e.g. instant porridge oats) and then seeding with living yeast.
Mick Bajcar
Editor's note: the life cycle of this particular Drosophilid is interesting.  Those members who still have the booklet on Drosophila I produced for the BDG some years ago will appreciate this.  The first flies to hatch from the cultures of this species are predominantly female, with very few males if any.  Most people would use these flies as food and then use any subsequent flies as the next generation for their cultures.  However, what they are doing, in fact, is to remove the majority of females from culture, leaving only males which, for reasons best known to themselves, hatch at a later time, usually several days after most of the females, and it is for this reason that cultures fail.
Try using the first flies produced from each culture to seed your next.  I think you will find a big difference in your success rate.
John Skillcorn