Food sources, mineral redistribution, and excreta are some of the ways ants enrich their mound environment. Phosphorus excretion has not been reported in red imported fire ants, Solenopsis invicta Buren. Quantification of phosphoric acid in worker fecal droplets and larval anal liquid of S. invicta was performed. Phosphoric acid was trimethylsilylated using N,O-bis(trimethylsilyl)trifluoroacetamide, and the tris(trimethylsilyl) phosphate was analyzed using gas chromatography-mass spectrometry. Phosphoric acid made up 2.13 ± 1.08% (SD) of the dry weight of worker fecal droplets and 2.09 ± 0.72% of the larval anal liquid. The rate of phosphoric acid production in workers was 0.08 ± 0.024 μg/ant/d. Because the hindgut of red imported fire ant larva is separated from the midgut, the excretory products in larval anal liquid are primarily of metabolic origin. The presence of phosphoric acid in larval anal liquid shows that red imported fire ants excrete phosphoric acid.