Fire ants self-assemble into waterproof rafts to survive floods

Mlot, Nathan; Tovey, Craig A.; Hu, David L.

doi:10.1073/pnas.1016658108

Cited by 232 publications

(233 citation statements)

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“…1E). The dynamics of formation of the escape drop and the ant raft has been studied with great detail (Mlot et al, 2011;Bonabeau et al, 1998;), and we now understand how the motion of ants within these structures leads to their distribution of sizes and shapes.…”

Section: Research Articlementioning

confidence: 99%

Fire ants actively control spacing and orientation within self-assemblages

Foster

Mlot

Lin

et al. 2014

Journal of Experimental Biology

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To overcome obstacles and survive harsh environments, fire ants link their bodies together to form self-assemblages such as rafts, bridges and bivouacs. Such structures are examples of self-assembling and self-healing materials, as ants can quickly create and break links with one another in response to changes in their environment. Because ants are opaque, the arrangement of the ants within these threedimensional networks was previously unknown. In this experimental study, we applied micro-scale computed tomography, or micro-CT, to visualize the connectivity, arrangement and orientation of ants within an assemblage. We identified active and geometric mechanisms that ants use to obtain favorable packing properties with respect to wellstudied packing of inert objects such as cylinders. Ants use their legs to push against their neighbors, doubling their spacing relative to random packing of cylinders. These legs also permit active control of their orientation, an ability ants use to arrange themselves perpendicularly rather than in parallel. Lastly, we found an important role of ant polymorphism in promoting self-aggregation: a large distribution of ant sizes permits small ants to fit between the legs of larger ants, a phenomenon that increases the number of average connections per ant. These combined mechanisms lead to low packing fraction and high connectivity, which increase raft buoyancy and strength during flash floods.

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Section: Research Articlementioning

confidence: 99%

Fire ants actively control spacing and orientation within self-assemblages

Foster

Mlot

Lin

et al. 2014

Journal of Experimental Biology

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“…The capillary bridge between two structured surfaces is very important in research into, and application of, micromechanical structures, surface mount technologies, microfluid dynamics, biological bionics, and other technical fields (Stewart et al, 2013;Bowden, 1997;Gau et al, 1999;Mlota et al, 2010;Saad and Neumann, 2014). The forces exerted by the liquid bridge have a great effect on the life and reliability of microelectromechanical systems (MEMS), flip-chip alignment, and the mobility of fluids in micro-channels (Guo et al, 2009;Chen and Soh, 2008;Bush et al, 2010;Dalin et al, 2010;Krammer, 2014).…”

Section: Introductionmentioning

confidence: 99%

Shape and force analysis of capillary bridge between two slender structured surfaces

Zhu

Jia

et al. 2015

Mech. Sci.

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Abstract. When a capillary bridge of a constant volume is formed between two surfaces, the shape of the liquid bridge will change as the separation between those surfaces is varied. To investigate the variable forces and Laplace pressure of the capillary bridge, as the shape the bridge evolves, a pseudo-three-dimensional force model of the capillary bridge is developed. Based on the characteristics of the slender structured surface, an efficient method is employed to directly solve the differential equations defining the shape of the capillary bridge. The spacing between the plates satisfying the liquid confined within the hydrophobic region of the structured surface is calculated. The method described in this paper can prevent meshing liquid surfaces such that, compared with Surface Evolver simulations, the computing speed is greatly improved. Finally, by comparing the results of the finite element simulations performed with Surface Evolver with those of the method employed in this paper, the practicality of the method is demonstrated.

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“…7 Though individual ants flounder at the interface, ant rafts, comprised of thousands of individuals, are able to stay afloat for months in the flood-prone rain forests of Brazil. 8 Might such interfacial organisms, as individuals or a collective, exploit flexibility to support a greater load?…”

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“…The behavior in the limits of large and small plates is deduced by considering the dominant terms in (7) and (8). For small plates, the force and torque balances become, respectively: 2βD ≈ H √ 4 − H 2 and 4k s α + Dβ 2 cos α ≈ β cos α H √ 4 − H 2 + β sin α H 2 − 2 .…”

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“…Nevertheless, our study does provide some insight for three-dimensional objects such as capillary rafts. Vella et al 16 noted that capillary rafts comprised of many particles exhibit elastic behavior, and inferred effective values of the Young's modulus and Poisson ratio for rafts comprised of various materials, Similarly, Mlot et al 8 inferred the effective constitutive properties of the ant raft. Our study indicates the manner in which flexibility assists the flotation of these rafts.…”

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Can flexibility help you float?

Burton

Bush

2012

Physics of Fluids

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We consider the role of flexibility in the weight-bearing characteristics of bodies floating at an interface. Specifically, we develop a theoretical model for a twodimensional thin floating plate that yields the maximum stable plate load and optimal stiffness for weight support. Plates small relative to the capillary length are primarily supported by surface tension, and their weight-bearing potential does not benefit from flexibility. Above a critical size comparable to the capillary length, flexibility assists interfacial flotation. For plates on the order of and larger than the capillary length, deflection from an initially flat shape increases the force resulting from hydrostatic pressure, allowing the plate to support a greater load. In this large plate limit, the shape that bears the most weight is a semicircle, which displaces the most fluid above the plate for a fixed plate length. Exact results for maximum weight-bearing plate shapes are compared to analytic approximations made in the limits of large and small plate sizes. The value of flexibility for floating to a number of biological organisms is discussed in light of our study. C 2012 American Institute of Physics.

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Fire ants self-assemble into waterproof rafts to survive floods

Cited by 232 publications

References 34 publications

Fire ants actively control spacing and orientation within self-assemblages

Fire ants actively control spacing and orientation within self-assemblages

Shape and force analysis of capillary bridge between two slender structured surfaces

Can flexibility help you float?

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