9.1. Introduction

Fluorescence in situ Hybridization (FISH) is a sensitive and specific method for localizing expressed genes or microbes within tissues of the honey bee. In general, a probe matching a specific DNA or RNA sequence is exposed to prepared tissues. This probe can then be localized using fluorescent tags, pointing the researcher to the precise location of a desired target. To date this method has been used successfully to show the locations of bacterial associates of bees (Martinson et al., 2012, Yue et al., 2008, and below).