Why buy fruit fly pupae? It is so much easier and cheaper just to culture fruit flies yourself. Then you have a constant supply and can use them as needed.
Pupa don't last long in the fridge. If you only have a few mantises you have to buy small amounts frequently in order for that to work, buying in bulk is a waste because they stop being viable long before you can use them all. In general, I have found the smaller the fly the less time the pupa stay viable in the fridge. Stable flies only stay good about 5 to 7 days and houseflies stop hatching after about 7 to 10 days in the fridge. Bluebottle fly pupa seem to last the longest, about 3 or 4 weeks then viability starts to drop dramatically after that. So you should never buy more than what your mantises can eat in the viability time period (allowing for at least half to be duds.) One way to stretch the time period is to hatch as many as you can toward the end when they are still mostly viable and keep them in deli cups with food and water. Adult flies can live a few weeks if you take care of them.
I would culture houseflies and bluebottle flies if I could but from what I've heard it's a rather disgusting and smelly venture. Instead I buy bluebottle fly pupa but I also raise various other prey so I don't have to buy the bb pupa so frequently. Besides the fruit flies I culture for my nymphs, I also have a colony of red runner roaches and a colony of black soldier flies. I also buy wax worms and mealworms that I feed as both larvae and as adults.
I wasn't even aware of any companies that sold fruit fly pupa, most sell cultures or adult flies. What you can do now that you have so many pupa about to go bad very soon is to let them hatch into adult flies in a separate container then start your own culture. You can get a recipe for fruit fly medium on this forum
here or you can buy a pre-made mix. Put the medium in a deli cup with a fabric lid along with some excelsior or netting for the flies to climb on and away from the gooey medium below. Then add all your hatched flies. You can put adult flies in the fridge for minute or two to knock them out and make them easy to handle. When that culture is near finished producing simply make a new one.
