Condensed Matter Seminar

Wed, 10/24/2012 - 16:00 - 17:00
Daniel Goldman, Georgia Tech

"Ant dynamics: digging, falling, and jamming in wet granular environments"

Colony members of the ~1 mm fire ant (Solenopsis invicta) collectively construct complex nests in a variety of soils. Nests consist of networks of tunnels connecting subterranean chambers, and are constructed through repeated excavation and deposition of grains or soil pellets. To discover principles of environmental interaction which allow rapid nest construction, we perform laboratory experiments in quasi-two-dimensional arenas filled with small wetted glass particles. The apparatus allows visualization of both the ants and the excavated substrate. We observe that excavated area and topological nest features such as edge-vertex scaling and degree distribution of the tunnel network are independent of body size of worker groups. We thus hypothesize that rules for construction of certain morphological features of the nest are “pre-programmed”. Observation of movement of ants in these tunnels reveals that locomotion is rarely smooth, but repeated slips occur during ascending and descending climbs. However, ants rapidly arrest these slips using antennae, limbs and body parts to jam and stabilize falls. Monitoring jamming events during controlled perturbation experiments imply that the ants engineer their environments to simplify the task of moving within.

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