Submitted to: Sociobiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/3/2007
Publication Date: 6/1/2007
Citation: Vogt, J.T., Smith, W.A. Effects of simulated and natural rainfall on summer mound construction by imported fire ants (Hymenoptera: Formicidae). Sociobiology. 2007.
Interpretive Summary: Little is known about how short term weather phenomena influence fire ant mound building activity and mound visibility as they relate to remote sensing. During hot, dry summer conditions, rain only stimulated mound surface repair, but the combination of lower temperatures and rain in the fall caused increases in mound height and volume. This new information will help guide researchers and others who are interested in precisely timing remote sensing efforts to detect fire ant mounds when they are largest and most visible from the air.
Technical Abstract: Imported fire ant (Solenopsis richteri x invicta) mounds in northeastern Mississippi were subjected to four treatments from late July through early September, 2006: application of water (7.5 L) and placement of an inverted 19 L bucket on top; application of water only; application of an inverted bucket only; and no treatment. Mound volume and height were measured prior to treatment and at 1 and 2 d after treatment. Condition of the mound surface was rated according to an index ranging from 0 (no evidence of recent building or repair activity) to 3 (recent building or repair activity over > 50% of mound surface). Treatments had small but significant effects on mound volume and height; in general, watering reduced volume over time (< 1 L) except in mounds that received an inverted bucket, and bucket placement had a slight positive effect on mound height while watering had a slight negative effect. Differences over time within treatments were very small (< 10 mm). The most significant effect was observed on condition of the mound surface, with the index increasing over time following application of water. Characteristics of S. invicta Buren (red imported fire ant) mounds were also measured over time under natural conditions from late July through mid-October, 2006. Mound height and volume were negatively correlated with temperature, and mound height was positively correlated with rainfall. The results of these studies indicate that in late summer, rainfall triggers mound rebuilding and repair but not a significant increase in size, which occurs as temperatures decrease into fall.