File:Pogonomyrmex barbatus - Red Harvester Ants. rain cover stack - 7.jpg

English: Red Harvester ants use any available dry grass, twigs and pine needle material that they are able to cut to size to construct protective mounds against rain over ventilation or secondary entry holes to the subterranean nest before rains. Thus the design of the mounds is very consistent, but the materials will vary. Many of these constructions will appear several days before rains indicating that these ants are highly sensitive to subtle changes in either humidity or air pressure or both.