This study provides a descriptive phenotype for the labor distribution within colonies of Odontomachus brunneus, a primitive Ponerine ant species. By describing the phenotype of the colony, we are able to indirectly assess the importance of the various mechanisms contributing to division of labor in this species. Specifically, we determined (1) what proportion of the colony is participating in foraging and (2) which individual members of the colony are foraging. To do this, the foraging population of ten colonies of O. brunneus was determined using mark-recapture methods. Additionally, entire colonies were excavated to determine total colony size and the locations of marked workers. Total colony size was used along with the mark-recapture data to determine the proportion of colony actively foraging. Relative age of workers by location was determined using fat extraction.
Results/Conclusions
Our results suggest that, in periods of high demand (i.e. brood production), the majority of O. brunneus adult colony members are actively involved in foraging regardless of age. This foraging population is distributed throughout the nest, though not evenly (Chi-square = 63.79, p = 0.0002). Perhaps the most interesting finding in this study is the propensity of female alates to forage alongside workers, which is highly uncommon for those species in which foraging behaviors have been documented.
We conclude that the foraging phenotype for O. brunneus may not fit cleanly into any one specific division of labor hypothesis. Similarly, a variety of traits pertaining to the division of labor in other Ponerine species (i.e. one third of the colony foraging in Neoponera apicalis and the switching of intra-colony tasks in Amblyopone pallipes) have been recorded suggesting that this primitive subfamily of ants may organize themselves in a different manner than their more derived counterparts.
