An Experimental Study of the Direct and Indirect Effects of Red Imported Fire Ants (Solenopsis invicta) on Monarch Butterfly (Danaus plexippus) Eggs and Larvae and the Arthropod Community on Milkweed Plants (Asclepias viridis)

Document Type


Degree Name

Master of Science (MS)


Biological and Environmental Sciences

Date of Award

Fall 2018


Monarch butterfly (Danaus plexippus) population declines have resulted in a strong interest in the potential effect of red imported fire ants (Solenopsis invicta) (RIFA) on the survival of monarch larvae during spring migration in the southern United States. The purpose of this study was to determine whether RIFA have direct impacts on monarch survival and to determine how RIFA might affect host plant community structure and indirectly affect monarch egg and larval survival. No direct effect of RIFA abundance on monarch survival was found when experimental manipulations of RIFA abundance were conducted. Plant arthropod richness, evenness, and effective number of groups were highest at intermediate abundances of RIFA, and arthropod richness was the best predictor of monarch survivorship. Monarch larvae surviving to the third instar occupied host plants with higher arthropod richness than did eggs or larvae that failed to reach the third instar. The results indicate that the presence of RIFA in moderate, naturally occurring abundances in the milkweed arthropod community improves monarch egg and larvae survival rates through indirect effects on community structure.


Jeff G. Kopachena

Subject Categories

Ecology and Evolutionary Biology | Life Sciences