Water is needed for metabolism and cooling, and is generally obtained by caged workers during ingestion of sugar solutions. In nature, water can also act as an important source of minerals (Brodschneider and Crailsheim, 2010), which can be highly variable depending upon source (WHO, 2005). In North America, for example, tap water provides important sources of calcium, magnesium, and sodium, at least for humans (Azoulay et al., 2001). It is not known how these differences may affect caged workers. Water is essential for maintaining worker honey bees in the laboratory. Carbohydrate solutions containing ≥50% (weight/volume) water are sufficient for hydration; if any less is provided, or if only sucrose paste is given, then a separate feeder containing tap water must be offered. Pre-trials for testing feeder leakage may be necessary due to the lower viscosity of water than sucrose solution. Tap water can be boiled to kill harmful micro-organisms, but it should be allowed to return to room temperature before it is given to caged workers.