Honeybee Apis mellifera swarms form large congested tree-hanging clusters made solely of bees attached to each other¹. How these structures are maintained under the influence of dynamic mechanical forcing is unknown. To address this, we created pendant clusters and subject them to dynamic loads of varying orientation, amplitude, frequency and duration. We find that horizontally shaken clusters adapt by spreading out to form wider, flatter cones that recover their original shape when unloaded. Measuring the response of a cluster to an impulsive pendular excitation shows that flattened cones deform less and relax faster than the elongated ones (that is, they are more stable). Particle-based simulations of a passive assemblage suggest a behavioural hypothesis: individual bees respond to local variations in strain by moving up the strain gradient, which is qualitatively consistent with our observations of individual bee movement during dynamic loading. The simulations also suggest that vertical shaking will not lead to significant differential strains and thus no shape adaptation, which we confirmed experimentally. Together, our findings highlight how a super-organismal structure responds to dynamic loading by actively changing its morphology to improve the collective stability of the cluster at the expense of increasing the average mechanical burden of an individual.

蜜蜂蜜蜂蜂群形成大型拥挤的挂树簇，完全由蜜蜂彼此附着构成¹。在动态机械力的影响下如何保持这些结构尚不清楚。为了解决这个问题，我们创建了悬垂簇并将它们置于方向，振幅，频率和持续时间各不相同的动态载荷下。我们发现，水平摇动的团簇可以通过散布形成更宽，更平的圆锥体来适应，这些圆锥体在卸载时会恢复其原始形状。测量簇对脉冲摆激励的响应表明，扁平圆锥体比细长圆锥体变形少且松弛快（也就是说，它们更稳定）。基于粒子的无源组件的模拟提出了一种行为假设：单个蜜蜂通过使应变梯度上移来响应应变的局部变化，这在质量上与我们对动态加载过程中单个蜜蜂运动的观察一致。模拟还表明，垂直摇动不会导致明显的差异应变，因此也不会产生形状适应性，我们通过实验证实了这一点。总之，我们的发现强调了超生物结构如何通过主动改变其形态来改善簇的集体稳定性，而以增加个人平均机械负担为代价，从而对动态载荷做出反应。