In the diagram, the variation illustration is

In the diagram, the variation illustration is morphological. Morphological variation refers to differences in physical characteristics or traits among individuals of a species. In the diagram, the variation is shown through differences in the size, shape, and coloration of the beetles. These physical differences are morphological in nature and can be used to distinguish one type of beetle from another. The other options are not applicable to the illustration shown in the diagram. Discontinuous variation refers to traits that are either present or absent, such as blood type, and is not applicable to morphological differences between beetles. Physiological variation refers to differences in the internal functions of an organism, such as metabolism or hormone production, and is not visible in the diagram. Biochemical variation refers to differences in the chemical composition of an organism, such as enzymes or proteins, and is also not visible in the diagram.