Submitted to: Journal of Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/18/2007
Publication Date: 1/1/2008
Citation: Vogt, J.T., Wallet, B., Coy, S.E. Dynamic Thermal Structure of Imported Fire Ant Mounds. 12pp. Journal of Insect Science 8:05, available online: insectscience.org/8.05. 2008.
Interpretive Summary: Much time and effort is expended to detect and count imported fire ant mounds over large areas for research and regulatory purposes. A study was conducted in Mississippi to determine daily and seasonal patterns in the temperature of fire ant mound surfaces, to assess the feasibility of using airborne thermal infrared imagery in remote sensing programs to detect and count mounds. Predictable changes related to mound shape and sun position were detected in mound surface temperature. These results will help researchers to optimize the timing of flights to obtain thermal infrared imagery, and the new data on predictable changes in mound surface temperature will help insure accurate identification of mounds in the images.
Technical Abstract: A study was undertaken to characterize surface temperatures of imported fire ant (Solenopsis invicta Buren, S. richteri Forel, and their hybrid) mounds as it relates to sun position and shape of the mounds, to better understand factors that affect absorption of solar radiation by the nest mound and to test feasibility of using thermal infrared imagery to remotely sense mounds. Mean mound surface temperature peaked shortly after solar noon and exceeded mean surface temperature of the surrounding surface. Temperature range (maximum temperature – minimum temperature) for mounds and their surroundings peaked near solar noon, and the temperature range of the mound surface exceeded that of the surrounding area. The temperature difference between mounds and their surroundings peaked around solar noon and ranged from about 2 to 10°C. Quadratic trends relating temperature measurements to time of day (expressed as percentage of daylight hours from apparent sunrise to apparent sunset) explained 77 to 88% of the variation in the data. Mounds were asymmetrical, with the apex offset on average 81.5 ± 1.2 mm to the north of the average center. South facing aspects were about 20% larger than north facing aspects. Mound surface aspect and slope affected surface temperature; this affect was greatly influenced by time of day. Average raster data were used to illustrate the effect of mound shape on surface temperature. Results indicate that the temperature differences between mounds and their surroundings are sufficient for detection using thermal infrared remote sensing, and predictable temporal changes in surface temperature may be useful for classifying mounds in images.