Metarhizium anisopliae infection alters feeding and trophallactic behavior in the ant Solenopsis invicta.

In social insects, social behavior may be changed in a way that preventing the spread of pathogens. We infected workers of the ant Solenopsis invicta with an entomopathogenic fungus Metarhizium anisopliae and then videotaped and/or measured worker feeding and trophallactic behavior. Results showed that fungal infected S. invicta enhanced their preference for bitter alkaloid chemical quinine on 3days after inoculation, which might be self-medication of S. invicta by ingesting more alkaloid substances in response to pathogenic infection. Furthermore, infected ants devoted more time to trophallactic behavior with their nestmates on 3days post inoculation, in return receiving more food. Increased interactions between exposed ants and their naive nestmates suggest the existence of social immunity in S. invicta. Overall, our study indicates that S. invicta may use behavioral defenses such as self-medication and social immunity in response to a M. anisopliae infection.