Figures are generally diagramatic in nature and require interpretation in order to apply them to actual specimens. A high level of understanding of nomenclature, morphology, anatomy, and distribution of the organisms under study is usually required for successful identification. Accuracy is directly related to the user's skill at interpreting morphological characters and variation. These keys are generally not designed for novices. Not all taxa, especially at the species level, can be identified in this way.
Some species are morphologically indistinguishable.
These cryptic species can only be separated by chemical methods. Have your specimen ready for identification. Microscope set up. Specimen positioned for observation. The key is comprised of numerous separate couplets.