Figure 3. Size-related change in shape of the frontal view of the head of Solenopsis invicta, plotted as the log ratio of the two allometric headwidths (HW1, HW2) to the isometric one (HW3) vs. the log of the body length. Headwidths 1, 2 and 3 are across the eyes, above the eyes and below the eyes, respectively (see Table 1). The outline drawings to the right are of a large worker (top, 1.2 mm mean headwidth) and small worker (bottom, 0.6 mm headwidth) scaled to the same size.