4.1.3. Age of adult workers used for laboratory experiments

Adult workers differ greatly in their physiology depending on their age. For example, changes in host immune response (Amdam et al., 2005a) and morphology (Rutrecht et al., 2007) over time can result in differences in disease resistance and susceptibility to parasites (Villa, 2007). Choice of age of experimental workers will reside solely on the purpose of the experiment, and is largely related to collection method (see sections 4.2, 4.3, 4.4). Researchers must ensure that experimental individuals are of a homogeneous age. If they are not, then heterogeneously aged individuals, or those of undefined age, should be evenly distributed among all cages.