6.2 Intra-species communication & Foraging in social insects  (Page 4/9)

A bee recruit must therefore decide which signals to follow in a particular situation, and the more the better. However, the more sensory input processed by the bee, the longer it takes to make a decision. This is called the speed-accuracy trade-off (Kulahci et al. 2008). A bee may therefore prefer to use a quicker single mode when foraging near a nest site, whereas when a food source is farther and more difficult to find, olfactory and visual signals can be used together, especially if the resource is highly profitable. This is called the efficacy trade-off hypothesis (Hebets&Rapaj 2005). Once learned, if the quality and benefit of the resource is high enough, it will outweigh the cost of increased sensory input (Kulahci et al. 2008). In Cameron’s study, even bumblebees were shown to mark profitable food sources with sucrose rewards to entice and recruit fellow foragers. What is interesting is that they were capable of interpreting these positive signals as negative once the food source had become unprofitable (1981). Scaptotrigona mexicana , a stingless bee species, can also associate the same pheromone marker as both a negative or positive signal depending on food source quality (Sánchez et al. 2008). They are thus able to interpret the same signal in different ways, suggesting the ability for individual decision-making and the capacity for experienced-based learning.

The honeybee’s (apis mellifera) waggle-dance

Bumblebees and stingless bees implement various modalities of communication but none are as advanced as the unique dance strategies of honeybees. Honeybees have evolved separate forms of communication that are influenced by their foraging and nesting environment and their brood size. A returning honeybee scout must communicate to the rest of the hive the location of a newly found food source or a potential nest site. They execute a ‘Waggle Dance’ where the scout performs quick forward moving abdominal vibrations as it crawls in straight line across the surface of the comb. It returns in semicircles of alternating directions to its starting place and then begins again a variable number of times (De Marco&Menzel 2005). It is an advertisement for the distance and direction of a new resource completed in a cyclical figure-eight pattern. Dance observers group closely together around the dancer, often coming in contact with her, thereby registering the source’s odor and often receiving samples of food that the forager has returned with (Hölldobler&Wilson 2009).

The length of the waggle phase depends directly on the distance to the resource. The longer the waggle face, the farther the resource is from the colony. The direction is also encoded in the angle of the dance (Von Frisch 1974)(De Marco&Menzel 2005). The returning foragers situate themselves on the ‘dance floor’ and begin a waggle phase in the direction of the food source with the sun as their azimuth. The length of the run is directly linked to the distance to the source (Beekman et al. 2008): the longer the tail-wagging period in the forward-moving part of the dance, the greater the advertised distance (Von Frisch 1974).