How to Join a Wave: Decision-Making Processes in Shimmering Behavior of Giant Honeybees (Apis dorsata)

Shimmering is a collective defence behaviour in Giant honeybees (Apis dorsata) whereby individual bees flip their abdomen upwards, producing Mexican wave-like patterns on the nest surface. Bucket bridging has been used to explain the spread of information in a chain of members including three testable concepts: first, linearity assumes that individual “agent bees” that participate in the wave will be affected preferentially from the side of wave origin. The directed-trigger hypothesis addresses the coincidence of the individual property of trigger direction with the collective property of wave direction. Second, continuity describes the transfer of information without being stopped, delayed or re-routed. The active-neighbours hypothesis assumes coincidence between the direction of the majority of shimmering-active neighbours and the trigger direction of the agents. Third, the graduality hypothesis refers to the interaction between an agent and her active neighbours, assuming a proportional relationship in the strength of abdomen flipping of the agent and her previously active neighbours. Shimmering waves provoked by dummy wasps were recorded with high-resolution video cameras. Individual bees were identified by 3D-image analysis, and their strength of abdominal flipping was assessed by pixel-based luminance changes in sequential frames. For each agent, the directedness of wave propagation was based on wave direction, trigger direction, and the direction of the majority of shimmering-active neighbours. The data supported the bucket bridging hypothesis, but only for a small proportion of agents: linearity was confirmed for 2.5%, continuity for 11.3% and graduality for 0.4% of surface bees (but in 2.6% of those agents with high wave-strength levels). The complimentary part of 90% of surface bees did not conform to bucket bridging. This fuzziness is discussed in terms of self-organisation and evolutionary adaptedness in Giant honeybee colonies to respond to rapidly changing threats such as predatory wasps scanning in front of the nest

‘Special agents’ trigger social waves in giant honeybees (Apis dorsata)

Giant honeybees (Apis dorsata) nest in the open and have therefore evolved a variety of defence strategies. Against predatory wasps, they produce highly coordinated Mexican wavelike cascades termed ‘shimmering’, whereby hundreds of bees flip their abdomens upwards. Although it is well known that shimmering commences at distinct spots on the nest surface, it is still unclear how shimmering is generated. In this study, colonies were exposed to living tethered wasps that were moved in front of the experimental nest. Temporal and spatial patterns of shimmering were investigated in and after the presence of the wasp. The numbers and locations of bees that participated in the shimmering were assessed, and those bees that triggered the waves were identified. The findings reveal that the position of identified trigger cohorts did not reflect the experimental path of the tethered wasp. Instead, the trigger centres were primarily arranged in the close periphery of the mouth zone of the nest, around those parts where the main locomotory activity occurs. This favours the ‘special-agents’ hypothesis that suggest that groups of specialized bees initiate the shimmering

Social Waves in Giant Honeybees Repel Hornets

Giant honeybees (Apis dorsata) nest in the open and have evolved a plethora of defence behaviors. Against predatory wasps, including hornets, they display highly coordinated Mexican wave-like cascades termed ‘shimmering’. Shimmering starts at distinct spots on the nest surface and then spreads across the nest within a split second whereby hundreds of individual bees flip their abdomens upwards. However, so far it is not known whether prey and predator interact and if shimmering has anti-predatory significance. This article reports on the complex spatial and temporal patterns of interaction between Giant honeybee and hornet exemplified in 450 filmed episodes of two A. dorsata colonies and hornets (Vespa sp.). Detailed frame-by-frame analysis showed that shimmering elicits an avoidance response from the hornets showing a strong temporal correlation with the time course of shimmering. In turn, the strength and the rate of the bees' shimmering are modulated by the hornets' flight speed and proximity. The findings suggest that shimmering creates a ‘shelter zone’ of around 50 cm that prevents predatory wasps from foraging bees directly from the nest surface. Thus shimmering appears to be a key defence strategy that supports the Giant honeybees' open-nesting life-style

Seasonal and daily variation of honeybee dancing temperature under constant feeding conditions

The seasonal and daily variation of the thorax temperature of dancing honeybee foragers, which gathered sucrose solutions from feeding places of constant quality (concentration and distance), was investigated by infrared thermography. Dancing temperature varied significantly between different days of the foraging season and depended on the time of day. In the morning and evening it varied much more than during the rest of the day. Part of this variation was caused by the hive temperature. The degree of cloudiness had no effect. In addition to intra-individual variations, some bees differed in the level of thermoregulation throughout the whole day (= inter-individual variation). Dancing temperature correlated neither with the stores of honey or pollen nor with the number of brood cells or empty cells. Since no correlation was found between the rate of recruited bees and dancing temperature it seems improbable that the dancers' body temperature acts as a predominant signal of food source profitability for the recruited bees

Behavioural features of a periodic form of massed flight activity in the giant honeybee Apis dorsata

A periodic form of massed flight behaviour in Apis dorsata was studied by video recording and image analysis. Two to three times a day the nest turns from the quiescent state into a high level of commotion for about 5 min. The vertical body orientations of the bees in the curtain then become more and more 'disordered'. In one nest, the total percentage of bees which flew off was less than 20% and the maximum number of hovering bees at a moment was 2-3% of the bee colony. Half of the curtain bees in the surface layer changed their position. The median moving index was below 0.3 mm/s in the quiescent condition and it rose up to 1.0 mm/s during massed flight activity. Our observations indicate that this kind of massed flight is quite different from the great defecation activities reported previously. Although there are diverse forms of massed flight activities in A dorsata, we found that this form of massed flight actitivity causes the periodical rearrangement of the roofing layer of curtain. On a Banyan tree we counted more than 100 nests of A dorsata and observed that nests of different areas of the tree did not supply bees or mass activity simultaneously