is an obligate ectoparasitic mite and the most important biotic threat currently facing honey bees (). We used neutral microsatellites to analyze previously unreported fine scale population structure of , a species characterized by extreme lack of genetic diversity owing to multiple bottleneck events, haplodiploidy, and primarily brother-sister matings. Our results surprisingly indicate that detectable hierarchical genetic variation exists between apiaries, between colonies within an apiary, and even within colonies.