Keith Barker, curator of the Bell’s genetic resources collection, gave a quick Q&A about our dermestids.
How long has there been a colony associated with the collections?
We have had dermestids off and on for a long, long time. Recently our colony had died down, but I got some beetles from the Science Museum and Sushma brought back some beetles from the Field Museum to kick start things again. The bulk of skeletal preps in our collection started in 1949, and were prepared by our previous bird curator Dwain Warner, so presumably the colony was started then. Since then, we have cataloged nearly 6,000 skeletal specimens, all prepared by feeding bird carcasses to beetles.
What are they eating these days?
They are eating birds most at the moment. They often also eat mammals, and sometimes fish. Colonies that eat a lot of fish seem to prefer that, colonies that eat birds and mammals likewise. They don’t like to switch. Generally, dermestids eat everything from swans to tiny warblers, deer skulls to shrews.
Any interesting facts to add?
It is very common for people working with beetles to eventually develop an allergy to them, so we wear personal protective equipment including a lab coat, gloves, and masks when working with the colony to prevent this.
Once cleaned, bones are stored in boxes for archival storage and available for research.
Dermestid beetles are ideal for getting soft tissue out of small, hard to reach bits. This is a small mammal in the process of being cleaned.
Dermestid beetle larvae on cardboard, a cheap substrate they can use to burrow.
A cleaned out skeleton of an American Woodcock (Scolopax minor).
Tiny bird and mammal skeletons being "cleaned" by dermestid beetles.
A salvage specimen of a white-tailed deer (Odocoileus virginianus) skull with antlers being actively cleaned by beetle larvae.
Sushma Reddy, Breckenridge chair of ornithology and our curator of birds, visited the colony recently to take some photos for us and offer her take on the beetles.
I think another interesting part of the story is the multi-week process of preparing skeletons. Dermestid beetles are still the neatest and cheapest way to clean out skeletons from carcasses. In birds and mammals, we usually dissect a carcass after taking some standard measurements by removing the skin/feathers/fur. For larger bodies we also take out some of the muscle and organs to make it easier for the beetles to get to the bones faster. Then we dry out the bodies—I was told it was because the beetles preferred decaying flesh, but others think the beetles don’t care. It’s not an exact science.
After a few days of air drying or freezer burning, the bodies are transferred to the beetle boxes. We place each body in a separate wire tray (usually custom made by the curatorial staff) or cardboard box because as the beetles gnaw away at the flesh, the skeleton may disarticulate, and we want to be able keep the bones together. It can take a colony anywhere from a few days to weeks to clean out a skeleton depending on its size. Then we have to remove the skeleton by shaking off the beetles and larvae as much as possible. As a second precaution, we usually bag and freeze each specimen to kill off any possible stowaways. A third precautionary step is to soak each skeleton in bleach to kill off any bacteria and such.
From my experience, each museum has its idiosyncratic improvised “equipment” for these processes. At the Bell Museum we have a large (100+) collection of yogurt containers that we use for the soaking process. As Keith once said, “Someone ate a lot of yogurt to help out the collection.” Finally, we wash out the skeletons in water to remove bleach (which can continue to corrode the bones otherwise) and pick out the bones to dry and then store in small boxes in the collections cabinets.
In some cases, someone will carefully write the catalog numbers on the large bones so that when scientists lay out the bones in a comparative series they don’t get mixed up. Being able to write neatly and in small type is a disappearing skill—at the Field Museum, they had a lone octogenarian volunteer who came once a week to do this one task. We need to find the Twin Cities equivalent.
We can maintain a colony in a large aquarium tank or rubbermaid box for several years with minimal maintenance. They only need a bit of substrate to burrow into, flesh to eat, water to drink, and warm temperatures to be happy.