Minimal intraspecific aggression among tawny crazy ants (Hymenoptera: Formicidae) in Florida

Authors: LAWSON, KATY - Former ARS Employee; Oi, David

Submitted to: Florida Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/5/2019
Publication Date: 6/8/2020
Citation: Lawson, K.J., Oi, D.H. 2020. Minimal intraspecific aggression among tawny crazy ants (Hymenoptera: Formicidae) in Florida. Florida Entomologist. 103(2):247-252. https://doi.org/10.1653/024.103.0215.
DOI: https://doi.org/10.1653/024.103.0215

Interpretive Summary: The tawny crazy ant, is an invasive ant from South America that infests Florida and Texas and is spreading to states along the Gulf Coast. Extremely large populations of this ant inundate urban and natural landscapes resulting in mass intrusions into buildings as well as reductions in biodiversity. Research conducted by the USDA-ARS Center for Medical, Agricultural, and Veterinary Entomology, determined that tawny crazy ant did not fight with other tawny crazy ants from different nests located at the same site as well as nests from distant (23 - 270 miles) locations within Florida. In fact, small fragments of colonies, including queens, from distant nests congregated together in artificial nests in the laboratory. This lack of aggressive behavior between widely separated colonies indicated that tawny crazy ants are not territorial over large areas. Lack of territoriality allows for the sharing of resources and movement of worker ants and brood between colonies, which can facilitate the spread of natural enemies such as pathogens as well as toxic baits used for their control.

Technical Abstract: Tawny crazy ant, Nylanderia fulva (Mayr), (Hymenoptera: Formicidae) are an invasive species found in states along the Gulf Coast of the USA. Their large populations are aggressive and can displace ant species already present in the area. Because tawny crazy ants are not territorial toward their own species within a locality, it was hypothesized that they may exhibit unicoloniality in their invasive range. To test this hypothesis, tawny crazy ants from separate locations in Florida were confined in small, enclosed arenas and their interactions were observed and documented using a rating scale of aggression behaviors. Carbohydrate consumption can also affect aggression in ants, so starved and non-starved ants were tested separately. For non-starved ants, the level of aggression between worker ants increased if they were from different locations, but this interaction rarely escalated to fighting. When starved ants from different locations were given access to sucrose solution, the ants would exhibit trophallaxis rather than fighting over the food source. Queens from different colonies would quickly nest together. Thus, intraspecific aggression was not evident among tawny crazy ants collected from widely separated locations in Florida.