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

‘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

Biological flora of the British isles: Ulmus glabra

1. This account presents information on all aspects of the biology of Ulmus glabra Hudson (wych elm) that are relevant to understanding its ecological characteristics and behaviour. The main topics are presented within the standard framework of the Biological Flora of the British Isles: distribution, habitat, communities, responses to biotic factors, responses to environment, structure and physiology, phenology, floral and seed characters, herbivores and disease, history and conservation. 2. Ulmus glabra is a large forest tree, and often an important canopy tree in ancient and seminatural woodlands. It is primarily native to the north and west of Britainand much of mainland Europe. It is the only elm native to Ireland. It is the most distinct of the British elms in that it rarely suckers and sets abundant viable seed. Although found on limestone screes and cliffs, and hedgerows, it is primarily awoodland tree, especially on moist, basic soils. In many secondary woodlands, it often cooccurs with Acer pseudoplatanus and has ecological needs that are similar to Fraxinus excelsior. 3. Ulmus glabra has clusters of c. 25 hermaphrodite flowers appearing before the leaves on previous year’s growth. Seeds are wind dispersed, falling in April to July, but remain viable for only a few days. Nevertheless, seedling establishment can be abundant. Hybridisation with other northern European elms is common but hybrids are notoriously difficult to identify and therefore probably under recorded. 4. The health and survival of wych elm in Europe has been seriously compromised since the 1970s due to Dutch elm disease caused by the fungus Ophiostoma novo ulmi, transmitted by elm bark beetles (Scolytus spp.). To the south of its Scottish stronghold, many elms are reduced to small trees regrowing from basal sprouts or seeds. These trees tend to be reinfected once trunk diameter exceeds 10 cm. Fortunately for its long term survival, seed production usually begins a number of years before they are reinfected