Meeting Abstract
Social insects work collectively to complete tasks; in many situations individuals can approach a task using different behaviors. For example, fire ants (S. invicta ) which inhabit subterranean nests covered by a hemispherical mound of soil permeated by narrow (~1 body length wide tunnels) can engulf soft-bodied prey via manipulation of the prey, the mound, or both. Given that each ant can perform such manipulations and transport, how does the collective decide which approach to take? Laboratory housed fire ant colonies were offered diverse prey embedded with lead markers, including mealworms, crickets and shrimp. Ant-prey-soil interactions on the nest surface were recorded using overhead video and subsurface using x-ray imaging. Mealworms were collectively carried intact into the mound through a tunnel, and then disassembled within the mound; shrimp was dismantled into small pieces above the surface and carried to mound tunnels; crickets were buried after limb removal and then disassembled and moved into tunnels. Soil reconfiguration occurred in all cases. To systematically understand the hypothesized emergent behaviors, we devised a controllable food item from Semolina flour (a “suji”). The shape, size and brittleness of the suji was controlled via the cooking process. These experiments revealed that a brittle suji was more likely to be deconstructed into small pieces before transport into tunnels; less breakable suji was typically buried or transported intact to a tunnel(if the item was small enough). Individual ants involved in feeding exhibited heterogeneity in tasks which included food maneuvering, dissection and mound reconfiguration. We hypothesize that food characteristics (like hardness and size) select for appropriate individual behavior which gives rise to the different engulfment scenarios.
