Since I recently did a presentation on stored product pests, my brain has been stuck on the Dermestid beetles lately. These are a really cool group of beetles that infest food products from initial processing all along the food chain to residences, commercial kitchens, and more. They can be found in non-food products like pet and animal food, hides, feathers, and carrion. Not only are they a problem where food is stored and produced, but they can also be an issue in museums, zoos, even pharmaceutical plants.
The background:
Dermestids go by many names: warehouse beetles, cabinet beetles, hide beetles, museum beetles, carpet beetles, larder beetles, and more. That’s because there are around 60 species of Dermestids that commonly infest products. Like all beetles, they go through four life stages: egg, larvae, pupae, adult. Time to develop from the egg to adult stage varies based on food, temperature, and other conditions but is often between one and two months. Adults are relatively short lived (about one to two months) and in that time will drop around 100 eggs. The larvae do the majority of the feeding damage, they are voracious little eaters.
These are a few of my favorite Dermestids!
The problems:
Despite having a preference for high protein foods, many species will feed and be able to develop on grain products and sometimes dried vegetation. Anything with flour (flour has protein in it!), seeds, nuts, milk powder, or other items that aren’t thought of as high in protein. About ten years ago, there was a massive recall of baby formulation due to Dermestids. In residential situations, these are quite commonly found in bagged pet food, birdseed, and fish food. Not just that, they can get to animals that may have died in a crawl space, attic, or wall void. As their food source is limited (because they have eaten it and produced subsequent generations that are hungrily looking for more) they move into structures.
It’s not just dead mammals. Those overwintering populations of thousands of lady beetles, stink bugs, clusterflies, and others that don’t make it out in the spring and expire in the wall void or the attic are a perfect food source for Dermestids. Those unlucky people who get bees in their walls? If you only get the adults out and the colony with all the honey and wax and brood is still there… it’s now a buffet for the beetles to feast on.
They are cold tolerant. They can survive freezing temperatures for short periods of time. In a study on cold tolerance, they found eggs (the most tolerant stage) could survive over seven hours at -18oC (that’s slightly below 0oF). All that was just in a little petri dish with no food and no protection (scientists are so mean!). That means putting that bag of infested flour in your standard chest freezer will take a lot longer than eight hours because the entire bag needs to get down to that killing temp first, then add on eight hours.
Add on to the fact they are cold tolerant: they can diapause. That’s right, the little larvae can basically say, “you know, things aren’t great right now. I have no food, it’s too cold, and I’m just going to take a nap for a few months.” (Forgive the anthropomorphizing.) The Khapra beetle can diapause for two years. When conditions become more favorable, they “wake up” and go back to their regularly scheduled feeding.
They can be “good”. Museums and taxidermists use Dermestids to clean skeletons of all the skin, muscles, organs, and other juicy bits of a dead animal. This may not seem like a problem, but it is when you have hides, taxidermied specimens, and tons of other animal-based products in your museum that you DON’T want the beetles to get into. No one wants to be the one to explain how the Dermestids that are supposed to be cleaning the snake skeleton are now devouring the one of a kind sabertooth tiger hide on display.
The solution to preventing Dermestid issues are the same basic concepts of IPM for all pests. Monitoring is especially important to discover problems early, find hotspots, and target treatments for best efficacy. Inspecting areas with animal products and high protein food sources is key to find any sanitation issues that can be dealt with and contain what can be contained. Treatments can be tricky and need to be carefully evaluated and performed (again, want to explain how you ruined that sabertooth hide?). There are resolutions and if you need solutions, contact us here!
PS - If you are looking for a really great reference for the stored product beetles in North America, check this out.