Well I tried drying some beaver castor this week and checked on them about 3 days later. Apparently the flys had got to some of them and maggots were crawling around in them. I cleaned the maggots out the best I could and put them in the freezer. Do you think they are ruined? Next time flys are an issue I will just freeze fresh and dry later. Thanks for the help.

You’ll be fine especially since you caught it early.

yes freeze fresh and dry later

those fly larvae will be full of juice as well
Xcelent grubs for fishing with.....till your fingers have a wee odour
lesson learned about drying in summer

There should be no problem with flys when drying castor at any time of year.Dry in a ventilated shed.Dont dry outside since birds or animals will take them.
There should be no red membrane or fat on the castor.-peel that off when removing the castors.You also can remove it with your fingers if you cut the castors out with a knife.
Castors have to be clean.
Also,when hanging to dry string two 14 ga wires a couple inch apart, that way the castor pod wont touch each other when hung and will dry on the outside in a short time with no folds to attract flies.
When removing castors for drying and selling the castors should remain attached as a pair.

I dry mine in a dark room. Flys don't seem to like dark areas.