Appropriate particle size may be a critical characteristic for effective granular ant baits. We examined the particle size preference of six species of pest ants to an anchovy-based bait. We also examined head capsule widths of Argentine ants, Linepithema humile (Mayr) (mean = 0.54 mm), California harvester ants, Pogonomyrmex californicus (Buckley) (mean = 1.63 mm), red imported fire ants, Solenopsis invicta Buren (mean = 0.9 mm), and southern fire ants, Solenopsis xyloni McCook (mean = 0.76 mm) and compared them with the first and second most preferred particle size. There were differences between particle size of which the most mass was removed and of which there were more particles removed by ants. California Argentine ants, southern fire ants, and Alabama Argentine ants removed more 840 to 1,000-μm particle mass of the anchovy diet but had more visits to dishes containing 420 to 590 μm particles. California harvester ants and Allegheny mound ants, Formica spp., removed more >2,000 μm particle mass but visited dishes containing 1,000 to 2,000 μm particles more often. Red imported fire ants also removed more >2,000μm particle mass but visited dishes with 590 to 840-μm particles most often. Pharaoh ants, Monomorium pharaonis (L.), removed and visited 420 to 590-μm particles more than any other size. A linear regression model determined that particle size preferred by each ant species relates to forager head width. The majority of particles of commercial ant bait, including Amdro, Ascend, Award, Bushwhacker, Max Force with fipronil, and old and new formulations of Max Force with hydramethylnon, were 1,000 to 2,000 μm, but the majority of Niban particles were <420 μm. Altering the size of particles of toxic ant baits to fit the particle size preference of each pest ant species may increase the efficacy of ant baits.