I was just wondering how red imported fire ants behave in colder climates, how far do they go underground and would they come out if I disturbed the nest?
Some information on what ants do in the winter is here. A fair amount of research has been done on fire ant temperature tolerance as a way of predicting the limits of its invasive range. Typically, fire ants will not leave their nests to forage when the soil temperature is below ~15º C (~59º F). At lower temperatures they often go deep underground to protect themselves from the cold. However, this does not mean that they will not become aggressive if the nest is disturbed. When the sun is shining and the temperature is cooler, fire ants move to the part of their mound that is being hit by sunlight to warm up. So even if the temperature is relatively low, they may be present and active in the top of the mound. At much lower temperatures, they are most likely to be inactive in the deeper parts of the colony and probably will not come out even if the nest is disturbed. In the lab, fire ant mortality is high if kept at freezing or near freezing temperatures for several days. However, colonies of fire ants in the wild have adaptations for dealing with the cold and can live in places where the minimum temperatures drop well below freezing. To answer your question, fire ant response to disturbance will depend on how cold it is. At very low temperatures (below freezing), they are unlikely to come out if you disturb the mound. But just because they are not active on the outside of the mound does not mean that they will not come out if it is disturbed.
Here are some interesting papers on fire ant temperature tolerance if you want to read more:
James S. S., Pereira R. M., Vail K. M., and Ownley B. H. 2002. Survival of imported fire ant (Hymenoptera: Formicidae) species subjected to freezing and near-freezing temperatures. Environ. Entom. 31: 127-133.
Korzukhin M. D., Porter S. D., Thompson L. C., and Wiley S. 2001. Modeling temperature-dependent range limits for the fire ant Solenopsis invicta (Hymenoptera: Formicidae) in the United States. Environ. Entom. 30: 645-655.
Porter S. D., and Tschinkel W. R. 1987. Foraging in Solenopsis invicta (Hymenoptera: Formicidae): Effects of weather and season. Environ. Entomol. 16: 802-808.
Thanks for your question,
Ben Rubin & the AntAsk Team