Attempts were made to colonize Nasonia vitripennis, a common parasite of the house fly, Musca domestica, on the face fly, Musca autumnalis. One-day-old face fly puparia were exposed to 3-day-old or older parasites for 24 hours. The parasites had previously fed on either house fly or face fly puparia. Dissection of face fly puparia revealed that high mortality of first-instar parasite larvae occurred and that at the time of adulthood surviving parasites were unable to emerge from the face fly puparium. Dead adult parasites were recovered from approximately 25% of the exposed puparia.