ABSTRACT The use of pteromalid parasitoids for muscoid fly control is becoming increasingly common. Two species that are often recommended for releases are Spalangia cameroni Perkins and Muscidifurax raptor Girault and Sanders. This study was conducted to determine if the reduced suitability of freeze-killed pupae for Pteromalidae, particularly S. cameroni, is due to freezing, freezing duration, or the type of freezer used. Processing pupae through freezing had a considerably greater negative effect on rearing of S. cameroni than on M. raptor. Although freezing pupae did reduce M. raptor progeny production, there was no effect of length of storage or type of freezer used. Freezing pupae for 5 months resulted in significantly fewer S. cameroni progeny than freezing pupae for 2 weeks. Although not significant, pupae held in a frostfree freezer produced more progeny than those in a non-frostfree freezer. Measurements of weights of parasitized pupae over time indicated that freezing did not result in accelera...