Analytical microscopy methods for examining morphological characters and physiological properties in beetle mandibles

Numerous arthropod taxa incorporate metals such as zinc and calcium into their mandibles for exoskeletal reinforcement. The location and type of cuticular metals are potentially diagnostic taxonomic characters. The absence or presence of these metals cannot be determined through conventional light microscopy techniques. Similarly, the coating of specimens for scanning electron microscopy (SEM) conceals these cuticular metals. Images generated while utilizing a variable pressure SEM with backscatter detectors on uncoated specimens revealed distinct areas of metal incorporation at the tips of some coleopteran mandibles. Energy dispersive spectroscopy (EDS) detectors were utilized to determine the elemental composition of the metal-incorporated mandibles. These three techniques are compared with respect to their potential impact on taxonomic studies.