科研人员发现，尽管单个蚂蚁可能在水中挣扎，一群火蚁可以相互连接起来并拦截空气从而形成一个防水的筏。为了探索入侵红火蚁（Solenopsis invicta）如何形成这种筏，David Hu及其同事把500只到8000只的蚂蚁群投入到了水面上。这些蚂蚁迅速在水上聚集，在几分钟时间里就稳定下来，形成了一个饼状结构，其中大约一半的蚂蚁形成了一个浸入水中的单层，让其余的蚂蚁漂浮起来。这组作者报告说，在这些筏的下面截住的空气很可能增加了浮力并且防止了底层的蚂蚁被淹死。测试表明，这些蚂蚁通过相互咬住对方的下颚与爪从而连接起来，形成了类似于防水纤维的编织结构。当这组科研人员从一个筏的顶层一只一只地拿走蚂蚁的时候，底层的蚂蚁向上运动从而保持筏的平均厚度。这组科研人员提出，浸入水中的蚂蚁可能有能力感知有多少蚁群成员在水面之上行走。这组作者指出，在组成筏的时候，在筏的边缘的蚂蚁被邻近的蚂蚁拦截住，这提示这种看上去的合作行为可能依赖于强迫。（生物谷Bioon.com）
生物谷推荐原文出处：
PNAS doi: 10.1073/pnas.1016658108
Fire ants self-assemble into waterproof rafts to survive floods
Nathan J. Mlota, Craig A. Toveyb, and David L. Hua,c,1
Abstract
Why does a single fire ant Solenopsis invicta struggle in water, whereas a group can float effortlessly for days? We use time-lapse photography to investigate how fire ants S. invicta link their bodies together to build waterproof rafts. Although water repellency in nature has been previously viewed as a static material property of plant leaves and insect cuticles, we here demonstrate a self-assembled hydrophobic surface. We find that ants can considerably enhance their water repellency by linking their bodies together, a process analogous to the weaving of a waterproof fabric. We present a model for the rate of raft construction based on observations of ant trajectories atop the raft. Central to the construction process is the trapping of ants at the raft edge by their neighbors, suggesting that some “cooperative” behaviors may rely upon coercion.
