Automated measurement of ommatidia in the compound eyes of beetles

The size of the ommatidia that compose the insect compound eye is linked to visual capacity, physiological performance, and cell size. Therefore, rapid and reliable methods for measuring ommatidia can advance research on insect ecology and evolution. We developed an automated method to measure ommatidia in nail polish imprints of the eyes of three Carabidae beetle species using the widely available, free software ImageJ. Our automated method was equivalent to a traditional manual method in terms of accuracy but had the advantage of being 70 times faster. We provide access to our algorithm, which can be used to investigate biological phenomena ranging from the functional architecture of the compound eye to the cellular basis of the evolution of body size and metabolic rates.