This scanning electron micrograph shows the large round open mouth of the hookworm and its four wedge-shaped teeth or cutting plates – a large one either side of two smaller ones. At the bottom right of the figure is a small scale bar indicating a length on 25 micrometres (μm) on the figure. This can be used to measure the following approximate dimensions: width of head, 225 μm; width of mouth, 125 μm; length of small and larger cutting plates, 30 and 40 μm respectively.