Insect and arthropod specimens in clear resin are a valuable tool for teaching entomology both in the classroom and in public outreach. A team at Texas A&M University worked via trial and error to refine an efficient, cost-effective process for resin casting and has shared the instructions with the entomological community in the open-access Journal of Insect Science. (Photo originally published in Bejcek et al 2018, Journal of Insect Science.)

By Josh Lancette

Last summer, a friend sent me a picture of a tick he found feeding on him after a weekend in the woods. He wanted help identifying it, concerned that it could possibly be a blacklegged tick and potential vector of Lyme disease.

Josh Lancette

Unfortunately, it was a terrible picture, so I wasn’t much help.

I do know how my friend felt, though. I’ve gone through the process of finding a tick and searching the internet for help identifying what species it is and information on if I should be concerned about any possible diseases.

Correct identification of ticks and other medically significant arthropods is important, but it’s not always easy to do. And it’s not necessarily easy to learn how to do, either. Pictures don’t always do a great job of conveying size, and sometimes coloration can be off depending on the photo’s lighting. A picture might be worth a thousand words, but it’s still not the real thing.

One effective method for learning to identify insects is using specimens. To use specimens most effectively, a team of researchers developed a method of embedding insects and other arthropods in resin, a clear, hard substance that protects the specimen while also allowing a person to observe the its morphological details. The protocol for embedding the specimens was published in April in the open-access Journal of Insect Science.

“At Texas A&M University, we do extensive teaching and outreach regarding arthropods of veterinary and medical importance,” says Gabriel Hamer, Ph.D., senior author on the report detailing the process. “Specimens are particularly important for teaching students and the public techniques to identify different species. We have found with extensive utilization of teaching specimens that they easily become damaged, and they are often rare specimens that are difficult to replace.”

And that’s where the resin comes in. While specimens that are pinned or preserved in ethanol can be damaged with handling, specimens embedded in resin can’t be.

Furthermore, embedding in resin ensures that any potentially dangerous specimen, such as a tick or kissing bug that carries a virus or parasite, won’t be mishandled and hurt someone.

“The resin-embedding approach is one resolution to ensure the preservation of specimens to retain the ability to identify, minimize risk of handling infectious specimens, and to be more resilient,” says Hamer.

Steps involved in casting insects and arthropods in clear resin include (clockwise from top left) setting the specimens in resin under a fume hood, cutting the resin into blocks using a band saw, sanding the resin blocks using a belt sander, and polishing the resin blocks with a buffing wheel. (Photo originally published in Bejcek et al 2018, Journal of Insect Science.)

Developing the method for embedding the specimens didn’t come without some trial and error first, though.

“From 2013 to 2017, we experimented with multiple resin types, different molds, and different sanding and polishing steps,” Hamer and co-authors write.

Eventually, they settled on a process that worked best by producing quality results as cheap as possible, and they wanted to share that process with others.

“Once we developed the protocol with positive reviews from colleagues, we wanted to ensure others in the entomological field had access to our lessons learned and final protocol that we have developed,” says Hamer.

With the increasing worldwide incidence of vector-borne disease in humans and animals, being able to train the next generation of veterinarians, medical doctors, and entomology professionals with actual vector specimens is increasingly important.

Josh Lancette is manager of publications at the Entomological Society of America.