Figure 1. Comparison of the head widths (H.W.) among worker subcastes in fire ants.

Majors are considered the biggest workers, minors are considered the smallest, and mediums are intermediate in size between majors and minors. The heads of a major worker (left; 0.93–1.46 mm H.W.), a medium worker (center; 0.73–0.92 mm H.W.) and a minor worker (right; ≤ 0.72 mm H.W.) are shown.