Spatial differences in worker behaviors within nest for S. invicta

Background/Question/Methods

Solenopsis invicta has been extensively studied in North America as an invasive species that costs the U.S. over 5 billion each year in agricultural damage, medical damage and management costs.  Much is known about its preferred habitat, morphology, and physiology, however its behavior, especially regarding differences in frequency and type of contact, brood care and transport within the nest has room for study. The purpose initially was to determine the best methods for keeping the colony in an environment that was natural and comfortable, as well as keep viewing and filming of all subterranean area’s possible.  Ultimately the experiment attempts to determine a basis for the decision making process in brood transport and assess the factors that affect brood care behavior inconsistencies as well as determine if a difference in frequency and type of contact between workers in various areas of the nest is present. Also examined was a summary of discrete behaviors observed in S. invicta. This study was performed in a laboratory constructed colony made of hydrostone plaster.  The colony was made with all subterranean tunnels and chambers directly against the clear plastic side of the container to allow for viewing.  A surface area for free foraging is also present.  Ants were fed on a diet consisting of sucrose solution and Acheta domestica as a protein source. Behavioral observations were centered upon worker-worker interactions in all areas of the nest, and transport of brood within brood chambers, adjacent tunnels, main vertical tunnels leaving the surface using video recorded with a Sony Handy-cam DCR-HC96 with a wide conversion lens. Population determined by mark and recapture Lincoln–Peterson method.

Results/Conclusions

There was a significant difference in number of workers carrying brood along a vertical shaft away from surface in five minute intervals from time of disturbance. (p<.0001) There was also a significant difference in number of workers carrying brood along a vertical shaft toward surface in five minute intervals from time of disturbance. (p<.0001) Average speed of workers was 0.48 cm/s. Insight into caretaking behavior of such a cooperative animal community could reveal implications for the evolution of many social and eusocial species.