Preferential Cannibalism of Larvae in Queen-Right and Queen-Less Monomorium Pharaonis Colonies

Adrian looking in microscope

Students

2018
College

Faculty

Associate Professor

Project Summary

The hypothesis of my study was that pharaoh ant, or Monomorium Pharaonis, colonies would preferentially cannibalize different larval stages depending on whether or not queens were present in the colonies. I expected colonies with queens to prefer cannibalizing younger larvae because they had already invested resources into older larvae. On the other hand, I expected colonies without queens to prefer to cannibalize older larvae because younger larvae could still mature into queens, which would be needed in the colony.

The reason I designed this experiment was because while working with the pharaoh ant over the past couple years, I had seen workers eat larvae when under stressful conditions. However, it was unclear what exact stressors caused this response and what evolutionary benefit it had, if any, for the colonies to cannibalize larvae, considering it would seem to minimize their fitness and chances of survival.

Over the course of the summer, I set up eighteen replicate colonies taken from a colony of a homogenous genotype. I split the ants into colonies with and without queens and then subjected the colonies to various conditions. Six of the colonies were used as controls, six were exposed to twenty-four hours of light, and six were starved. From the data I gathered, the difference between whether a colony had queens or not and what stage of larvae the workers preferentially cannibalized was statistically significant. The colonies with queens tended to cannibalize the younger larvae and the queen-less colonies tended to cannibalize the older larvae. This followed my original hypothesis regarding the way the colonies would act.

Although I have worked with these ants for the past two years, it was a great learning experience to design my own experimental setup and see the experiment through to its completion. I had been wanting to plan an experiment about stress response in pharaoh ants for the past couple years, and it was great to finally be able to carry it out.  I am planning to use the data I have gathered over the summer as preliminary research for an independent study in the fall. In my future study, I intend to create more replicated colonies and streamline the research setup in order to hopefully confirm that the differences in behavior between colonies with and without queens are statistically significant. Overall, my experience this summer has allowed me to expand my organizational and research design experience as well as embark on a new topic of research, which I am excited to continue working on into the new school year.