The occurrence of a phytoseiid mite Typhlodromalus peregrinus (Muma) (Acari: Phytoseiidae), over-wintering in rosette bud mite Tricetacus fraseri Amrine (Acari: Phytoptidae) galls is documented with parameters, including aperture size and morphological features, influencing the occupation of rosette bud mite galls by this predator during the winter months. Observations are made on utilization of T. fraseri as a winter food source for T. peregrinus. This paper also reports on the over wintering stage of T. fraseri. Studies were conducted in a single commercial Fraser fir tree plantation in Ashe County, N.C. during the winter of 2006-7. Twenty-nine phytoseiid mites were found in 14 galls (10.6%). There was an average of 2 phytoseiid mites per gall and the highest number of phytoseiid mites in any one gall was 4. Gall heights, width, cavity depth, and aperture size (n = 121) averaged 7.4 mm, 7.4 mm, 2.1 mm, and 2.0 mm, respectively. The height, width, depth, and aperture size of galls containing T. peregrinus (n = 14) averaged 7.2 mm, 7.5 mm, 2.9 mm, and 1.6 mm, respectively. Typhlodromalus peregrinus was observed feeding on all stages of the rosette bud mite.