10.2 Parameters to consider when studying honey bee dance

Some dance parameters can vary according to the profitability of the food source. For instance, if the sugar concentration or the solution flow rate (sugar mass per time) change, the dance probability, the dance time and the dance tempo (the number of waggles or reversals per 15 s running on the comb) increase according to the energetic value of the exploited resource (von Frisch, 1967; Farina, 1996; De Marco and Farina, 2001). In the specific case of the waggle dance, the interval between two successive waggle runs (defined as the circle phase) is shorter for higher food source profitability (Seeley et al., 2000; Hrncir et al., 2011). Thus, an enhanced recruitment for higher food source profitability might be explained by a larger number of waggle runs per unit time inside the hive (von Frisch, 1967; Seeley, 1986; Fernández et al., 2003). A larger number of waggle runs per unit time attracts the attention of more bees located in the surrounding of the dance floor (Wells and Wenner, 1973) and motivates them to fly out. Once in the field, bees use the spatial information acquired while following the dance to arrive at the goal (Riley et al., 2005). Therefore, the higher the redundancy of the signal (higher number of waggle runs displayed) the higher the probability of transmitting the spatial information to nest mates and consequently the higher the recruitment level observed at the exploited food source.

However, the parameters recorded during the dance not only depend on the profitability of the resource discovered by the forager. These dance parameters also depend on the forager's own experience in the field (von Frisch, 1967; Gil and Farina, 2002), on the predictability of the food source in terms of profitability (Raveret Richter and Waddington, 1993; De Marco et al., 2005) and on the nutritional state of the hive (Lindauer, 1954; Seeley, 1989), amongst other factors (see Dyer, 2002 for a more detailed review).

The waggle dance of the honey bee Apis mellifera is, without any doubt, one of the best studied communication systems in the animal kingdom. Inexperienced recruits who follow the dances are capable of deciphering the vector information provided by the dancers' movements (the waggle runs) and can use this information when searching for the advertised patch (Esch et al., 2001; Riley et al., 2005). Furthermore, the information obtained from decoding the waggle dance is broad. This implies that other stimuli belonging to different sensory modalities are possibly being used. One possible additional source of information used by dance followers are the thoracic vibrations pulsed by the dancer while waggling (frequently referred to as "dance sounds"; Esch, 1961a, b; Wenner, 1962; Hrncir et al., 2011). The volatile compounds released by the dancers, which act as a "recruiting pheromone", are another additional source of information (Thom et al., 2007). The olfactory cues incidentally acquired while bees forage at flowers (Farina et al., 2005) are yet another source of information available to dance followers.

In other words, the honey bee dance should be considered a multi-component signal, i.e. a signal comprised of more than one informational component. These components can be redundant or not and can lead to an enhanced response, because the receivers (the dance followers) might acquires more than a single type of information. Thus, these signals can even provide multiple messages (for details see Grüter and Farina, 2009). Within this framework, the function of the waggle dance is not only to indicate the location of food sources but to attract surrounding bees, so that they can receive other types of information, i.e. it informs bees of the presence of good food sources, it activates self-acquired navigational information (if present), and it facilitates the acquisition of information about food odours.