Once insects are cleaned up (Step 1, previous blog), I run them through a dehydration series from 70% ethanol to 100% ethanol. This takes about 2 days for my small insects. Then they are immersed in HMDS overnight or critical point dried. It is important to remove all the water in the tissue because HMDS + water = ammonia gas. I have used both drying approaches, initially training on the Critical Point Dryer at the American Museum of Natural (a training story for another day). HMDS = Hexamethyldisilizane is a widely-used drying agent to prepare specimens for scanning electron microscopy study. I use the Sigma-Aldrich brand. For large insects, one could also do a first and second bath in HMDS, just to be sure there is not more water in the sample.
After a thorough bath, I open the caps of each vial to let the beetle sample air-dry. It is much nicer and safer to use a Desiccating Chamber (ScienceWare brand) at the lab, so I don’t have to smell the fumes as the HMDS vaporizes (which is a little dangerous, actually). I’ll let these beetle babies air-dry overnight before coating them tomorrow.
My insect colleagues at the California Department of Food and Agriculture in Sacramento have a detailed account of how we use this HMDS cleaning/drying method in an insect collection: https://www.cdfa.ca.gov/plant/ppd/entomology/HMDS.html
Citation:
Brown, B.V. 1993. A further chemical alternative to critical- point-drying for preparing small (or large) flies. Fly Times 11: 10.
Hazrin-Chong, N.H. & M. Manefield. 2012. An alternative SEM drying method using hexamethyldisilazane (HMDS) for microbial cell attachment studies on sub-bituminous coal. Journal of Microbiological Methods 2012-08-01.
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