Deciding on the wing: in-flight decision making and search space sampling in the red dwarf honeybee Apis florea

Abstract

During reproductive swarming and seasonal migration, a honeybee swarm needs to locate and move to a new, suitable nest site. While the nest-site selection process in cavity-nesting species such as the European honeybee Apis mellifera is very precise with the swarm carefully selecting a single site, open-nesting species, such as Apis florea, lack such precision. These differences in precision in the nest-site selection process are thought to arise from the differing nest-site requirements of open-and cavity-nesting species. While A. florea can nest on almost any tree, A. mellifera is constrained by the scarcity of suitable nest sites. Here we show that imprecision in the nest-site selection process allows swarms to quickly reach a decision when many nest sites are available. In contrast, a very precise nestsite selection process slows down the decision-making process when nest sites are abundant.Nest-site selection in A. florea appears to be more similar to search-space sampling than to a decision-making process. Bees appear to scout the environment for general areas in which potential nest sites are abundant. Bees involved in searching the environment for suitable nest sites are also involved in guiding the swarm once the decision to depart has been made. Generally A. florea swarms exhibit a lack of consensus in the direction indicated by dancers prior to take-off. Because of this lack of consensus a swarm of A. florea will need to determine its exact direction of travel while in flight. We show that in the absence of directional consensus a swarm of bees can still be guided towards an area containing suitable nest sites provided directional dissent is not too great and nest sites are abundant. However, if the swarm needs to move to a very specific location (a single point in space), directional dissent should be avoided, resulting in a more lengthy decision-making process prior to departure. We further show that the guidance mechanism of bee swarms, so-called 'streaking', functions both when directional dissent is present and when it is absent, making it a more general mechanism of group movement than previously thought.

Do small swarms have an advantage when house hunting? The effect of swarm size on nest-site selection by Apis mellifera

“…[6]) is to give swarms a choice between two to six nest sites (but see [39] for a modelling study with a choice between 120 distinct nest sites). Natural honeybee swarms are likely to be faced with a greater number of potential nest sites to choose between.…”

Moving without a purpose: an experimental study of swarm guidance in the Western honey bee (Apis mellifera Linnaeus)

“…Modelling studies have shown that such groups are able to compromise and head in a direction that is a middle ground between the two subgroups' locations (Leonard et al, 2012). Moving in the average direction also seems to be the tactic used by red dwarf honey bee (Apis florea) swarms, which often take to the air while still dancing for multiple locations (Oldroyd et al, 2008;Diwold et al, 2011;Makinson et al, 2011, and the giant honey bee Apis dorsata (Makinson, 2013). Both A. florea and A. dorsata build nests in the open and are rather tolerant with respect to where exactly they nest.…”

Honeybee linguistics—a comparative analysis of the waggle dance among species of Apis

“…When selecting a nest site, it is essential the bees all arrive at the same site. Studies on nest-site selection in A. florea have suggested that due to A. florea's nest-site requirements (basically a shaded twig on a tree) and the abundance of potential nest sites, A. florea swarms only decide on the general direction they need to fly in to (Diwold et al, 2011;Makinson et al, 2011;Schaerf et al, 2011). Hence, the angular deviation in the dance will not necessarily negatively affect the ability of A. florea swarms to move cohesively to a new site (Diwold et al, 2011).…”

“…Studies on nest-site selection in A. florea have suggested that due to A. florea's nest-site requirements (basically a shaded twig on a tree) and the abundance of potential nest sites, A. florea swarms only decide on the general direction they need to fly in to (Diwold et al, 2011;Makinson et al, 2011;Schaerf et al, 2011). Hence, the angular deviation in the dance will not necessarily negatively affect the ability of A. florea swarms to move cohesively to a new site (Diwold et al, 2011). A. dorsata most likely uses visual cues to locate potential nest sites, as these bees prefer to nest in aggregations, mostly in trees that stand out in the environment or on conspicious buildings such as water towers or spires of temples (Oldroyd and Wongsiri, 2006).…”

“…So far the only other Apis species on which some data have been collected on dance precision is A. florea in the context of nest site selection Makinson et al, 2011). These studies seemed to suggest that the nest site dances of A. florea are less precise than the nest site dances of A. mellifera which could potentially be explained by their different nest site requirements (Diwold et al, 2011;Schaerf et al, 2011). Here we look at dance precision amongst species of Apis in more detail.…”