6.5.1. Electric shock as an aversive stimulus
Electric shock is the most frequently used aversive stimulus, because it is easy to control. It is advisable to begin with the lowest effective intensity. If the shock is too intense, the bee will be damaged. Alternating current (AC) gives good results and direct current (DC) is also effective. There are no studies that test whether AC or DC current is more effective for honey bees. In addition, resistance measurements of several bees should be taken prior to conducting the formal experiments, for example by using a Volt meter. These measurements will provide an estimate of the amount of current that will flow through the bees. Shock can be applied in several ways depending upon the requirements of the experiment. For example, in a place learning assay, a grid based on the design of Kolmes et al. (1989) was effective (Agarwal et al. 2011). If the researcher wants to prepare grids from metal rods, the rods need to be cleaned, because oil or other material on the surface of the rods will interfere with the flow of current. If the use of a grid is not practical, antistatic foam is useful (Abramson et al., 2004). It has a number of advantages over other shocking surfaces including ease of construction and standardization. The major disadvantage is that the material is not transparent. If visual (or olfactory) stimuli are going to be used with antistatic foam, the stimuli cannot be presented beneath the bee.
Shock can also be applied to free-flying bees by using a modified landing surface constructed from conductive material. When the bee lands on the surface and extends its proboscis into an electrically isolated feeding well containing sucrose, the circuit is completed and the bee receives a shock (Fig. 7; Abramson, 1986). Another method to administer the shock that does not need the feeding well is to use the antistatic foam.