Nondestructive Imaging of Pin-Mounted Museum Insect Specimens Using the Field-Emission Environmental Scanning Electron Microscope (ESEM-FEG)

Abstract

The abilities of researchers to obtain high-quality images and other data from pin-mounted museum insect specimens using conventional scanning electron microscopy (SEM) are hindered by several necessary constraints. The specimens may represent unique exemplars (e.g., holotypes) upon which the taxon name rests. In some cases the specimen may no longer be extant in any environment outside the museum. Thus these insects must always be handled with extreme care,Tegardless of how they are to be observed.Normal preparation of an insect for SEM involves sputter coating it with a conductive metal to minimize the effects of charging, and conductive paint must be applied to an obscure or uninteresting area to complete the connection to the specimen mount and thus to ground. Generally, unless such specimens have been newly collected, they will have already been killed and allowed to air dry, with a mounting pin inserted through the thorax. The body of the insect shrinks against the pin, which cannot then be removed for observation and later reinserted without damage.