Friday, June 5, 2015

Queen of the Flies

*Note: contains images of animal skulls in various stages of preparation. Ick Factor medium. Just be glad this post doesn't come in Surround Smell-o-vision.

Ever had a Friday where you come into your office and wonder "Where the heck did these bloody flies come from?"

No? Just me?

I'm really not surprised by that. I have a rather odd science-related side project at the museum: I maintain a dermestid colony.

What are dermestids? Dermestid beetles (and these guys are actual beetles, being part of the Order Coleoptera, or "sheathed wing" beetles with a hard outer wing covering) are scavenger beetles of the genus Dermestes: they are also known more colloquially as "flesh-eating beetles" or skin beetles.

These beetles aren't flesh-eating like the stylized movie scarab beetles in "The Mummy". These beetles are scavengers: you would have to be quite dead in order to attract the interest of a dermestid beetle. In fact, the Dermestidae are important in the realm of forensic entomology, as their presence on a body (for example) is an indicator of how long it has been exposed.

Dermestidae are considered by the non-natural history person as a commercial and household pest: they can be found infesting pantries, shipments of dried protein (pet food is commonly afflicted), and any place where humans (and their pets) cook, eat, drop a bit of food, shed, store food...the most common place to find dermestid beetles in your home (yes, you have them) is in pet foot areas, under ovens, along baseboards on floors, and in the tracts of windows - basically any place where food, hair, and other dead insects accumulate.

The most common dermestid beetle you will see in your home (at least, in Canada) is the larder beetle (Dermestes lardarius). Having these beetles in your home doesn't mean that your home is dirty (although if you seem overrun with them, you may want to call a pest management expert); these beetles are a natural part of Nature's clean-up crew.
Adult larder beetle.

Larval larder beetle. Royal Alberta Museum.

Although Dermestes are considered a pest, it is uncommon for natural history museums to keep a colony of dermestids. These beetles are an important part of a museum's research team, as they very happily clean tissue and skin off of bones, leaving the bones to be cleaned, archived, and used in a variety of research and outreach projects. The most common beetle I have heard of employed (they literally work for jerky) at museums is Dermestes maculatus, the hide beetle. Museums and labs that I know of that use dermestids are the Royal Ontario Museum and their skin beetles, the American Museum of Natural History, and the Witmer Lab at Ohio University, to name just a few.
Adult hide beetle.

I started a wild-caught dermestid colony as an experiment I fully expected to fail. I scoured my home for a few larder beetles, and persuaded friends to find larder beetles in their homes. I had a grouse specimen (road kill) that I had left to dry in the basement of the museum, and placed the grouse mummy in the box with the dermestids and a few layers of unbleached corrugated cardboard. Lo and behold, the larder beetles took to their work with great enthusiasm! I quickly expanded my one colony to three separate ones (Homeworld, Earth That Was, and Miranda), and was soon contacted by local wildlife authorities to clean some of their skulls that they had set aside as teaching specimens.

My beetles became something of local celebrities. Recently I was interviewed for CBC Radio Daybreak North about how dermestid beetles can help paleontologists with their research. The beetles have also made guest appearances for our summer education camps. It's no surprise that when you ask a room full of kids "Hey, does anyone want to see some flesh-eating beetles?" there will be several that say "EW! Yeah!"

While dermestids are thought to prefer dried tissue, they actually quite like wet tissues, but in the wild they are out competed by fly larvae. I experimented by putting in a whole thawed skull of a grey wolf, hide and all. I wanted to see how long it took my colony to clean a skull from start to finish.
Dermestid adults, busy at work.

I covered the skull with paper towel, as the beetles like to work under cover. Every few days we mist the paper towels with water, and the larvae and adults come out to drink.

It took almost a year (my colonies are small), but the beetles completely stripped the skull of all of the fur (in which they now burrow to pupate), and the hungry larvae ate all of the hide and tissue.

Dermestid beetle colonies are simultaneously simple and frustrating to manage. Since they love to eat, burrow, and pupate in dry organic material, they are a potential archives hazard. The room in which the colony is kept should be sealed so these little escape artists (which they are, under certain circumstances) cannot leave. Any specimens prepared using dermestids have to be quarantined in a freezer for a few weeks to kill any remaining adults, larvae, and eggs. They will climb if there is ANY texture at all on the inside walls of their colony container: I went through three types of plastic bins before I found one with smooth enough sides to foil these tenacious scavengers. If you use an old aquarium, they will climb up any of the silicone sealant used on the corners. The adults fly at temperatures above 20 degrees Celsius, so the colony container must have a lid. Since the colony container needs both a lid and air, the colony ventilation must be such that other members of Nature's clean-up crew, specifically flies, cannot enter. This is where we start today's adventure.

Recently I added a fresh skinned wolf head and a great grey owl head to Miranda Colony, which was already processing an adult black bear. I've been in and out of the office for the past three weeks, and every time I peeked in on the colonies, they were doing well. Smelly, but well. So, I figured I would let them alone for a week before I went in to disturb them. Today I noticed a big black fly in my office, buzzing around like a B52 Bomber. Rather annoyed at this, I swatted it and gave it no more thought...until a second fly buzzed its way in. Hmm. Flies plus dead tissue...uh oh. I poked my head out of the office, and the hallway light in front of the dermestid room had several flies on it. I went in and saw this in Miranda Colony:

After almost three years of never having a fly infestation here I was, Queen of the Flies. This called for immediate action. Taxidermy forums suggested hand-picking maggots and eggs off of the skulls, but, my Dear Readers, I LOATHE maggots with a burning passion that will never die. I went for option #2: freeze the suspect skulls, muck out the colony, and seal it off until all the flies have emerged and died.

I needed supplies. I flew (haha) to the local dollar store and picked up these:
Yeah...this group of purchases doesn't look sketchy at all!
The nylons and duct tape were for constructing new, fly-proof container lids. The garbage bags were for the contaminated skulls. The jerky dog treats were for the newly cleaned colony: the dermestids will eat them, but the flies will have little use for them. The fly-swatter is self explanatory.

I hauled all of the colonies outside to inspect them. Homeworld and Earth That Was had no traces of either adult flies, pupae, or larvae in the container (that I could see). Here's a young black bear skull, full of nothing but dermestid larvae and adults.

Both Homeworld and Earth That Was received new nylon lids. Until I can find larger sections of nylon, these lids are taped down to hold them in place. They will be more of a hassle to use when I need to access the colonies, but for the time being they will keep out any remaining flies that may be buzzing around. Another benefit is that these nylon lids will keep any flies that I may have missed contained within the respective colonies. I don't need any more trouble makers flying around my bug room.

I moved on to Miranda colony. Sure enough, several adult flies were in there. I picked those out and examined the skulls. The (not so) fresh wolf skull contained damning evidence: fly pupae.
Adult and larval larder beetle at top of the image, fly pupae at the bottom.

After being picked off and thrown in the trash, every skull in Miranda Colony was deposited into a heavy duty garbage bag. They are now all suspect, and all need to be quarantined.

Great Grey Owl head.
Adult black bear. This skull is about 3/4 finished. It's likely the flies would have no interest in the remaining dried tissue, but it's headed (pun totally intended) for the freezers.

Once the skulls were removed and double-bagged, I removed all of the loose bedding and towel covers. I stripped the colony down to its bare essentials, leaving the cardboard in which the dermestids like to burrow, and the layers of detritus they have built up.

Since the remaining dermestid adults and larvae still need to eat, I added the dog treat jerky. The dried meat will be of little interest to the flies, but will keep the dermestids well fed.

Once I added the jerky (the dermestids found it right away), I sealed up the container with a nylon lid. I also added an X to the side, just to remind me that this is the colony under surveillance. It didn't take long for two more flies to emerge.

With the colonies under control, I added the bagged skulls to the freezer. In this case, I'm not too worried about freezer burn.

What's next? I'll be monitoring all three colonies closely. Any flies that emerge will not be able to escape and infest the neighboring colonies, and any flies emerging will be removed. If I find flies in Homeworld and/or Earth That Was, those skulls will join the others in the freezer for quarantine. Freezing will also kill any dermestid eggs and larvae on the infested skulls, but this is an acceptable loss to avoid turning my work area into a scene from Amityville Horror.

I find all of this rather embarrassing. My colonies have been functioning without such an infestation for around three years, even with fresh specimens. Fortunately it is a short-lived problem, and I caught it early.

Stay tuned for more Adventures of Dermestia, Mistress of the Flesh-Eating Beetles! Will she win her battle against her dark alter ego, Queen of the Flies?

UPDATE 07-June-2015:

Well, my friends, the Queen of the Flies has been elevated to the Empress of Flies. My fly containment system has worked - to a point. Unfortunately Earth That Was has fallen to the scourge of all that is fly, and new flies have appeared in that colony. There were so many flies trapped in Miranda that I put that colony outside (it's above freezing here at night now, so there is no danger to the dermestids).

What will I do now? Tomorrow I will do a full colony strip-down and rebuild of Miranda and Earth That Was. Time to start fresh, so to speak. This will entail:
1. Removing and freezing skulls in Earth That Was.
2. Salvaging as many of the adult and larval dermestids as possible from each colony in separate containers.
3. Binning all of the comfy detritus the dermestids have built up for themselves. No matter how carefully I sift, I risk missing fly eggs, larvae, and pupae.
4. Wash out the two containers. Let air dry.
5. Lay down new corrugated cardboard and new polystyrene foam (they LOVE to burrow into the foam for pupating).
6. Add salvaged beetles.

I'll post an update on the salvage work tomorrow or the next day.

Until then,
Empress of Flies.

UPDATE 11 - June - 2015:

I have, for all intents and purposes, rebooted Earth That Was and Miranda. To date Homeworld remains fly-free.

After we removed the young black bear skull, a Purple Finch, and the legs of a Great Horned Owl for quarantine in the freezers, my lab tech Linda and I hand-picked as many adult and larval dermestids as we could find. All of their bedding (and any beetles that refused to be found) had to be binned. We saw several fly pupae during the beetle picking.

Adult larder beetles, ready to be pioneers in their new home.

We placed our rescued beetles in clean 5 gal. buckets with pieces of corrugated cardboard, dry cat food, and turkey jerky treats (for dogs). The larvae will burrow into the cardboard to pupate.

Close-up of the larder beetles examining their new food.
We closed off the lids of the rescue colonies with several layers of cheesecloth, and thoroughly cleaned the old colony containers. Once the skulls are out of quarantine, I can transfer the beetles and the skulls back to the larger containers.

Rescue colonies for Earth That Was and Miranda.
So far the beetles in all three colonies are doing well. They have an appearance to make during the inaugural weekend (June 27-28) for the Tumbler Ridge Geopark.

Stay tuned!

UPDATE: 18 August 2015 - Response to Comment

Since I am having internet issues with the comments section, I will respond to the latest comment from Dermy/compostguy101 in the text of the blog. One of the great parts of having experiment colonies is having lab notes!

My response:
Thank you for your interesting comment. These colonies are experimental colonies of wild-caught Dermestes lardarius from the region. These colonies are set up to test the "preferences", if you will, of these beetles for osteological specimens in various stages of prep.

In my description of the observations I've made from 2010-2015, I'll be using terms that appear anthropomorphic, but it's how the curators/techs at the museums I consult with refer to their beetles, and it's done with the understanding that it's in jest. While it appears to be common knowledge that dermestids require fully dried specimens to process, my observations of the colonies for a few years have shown that dermestids do quite fine with "fresh" material - a dose of ethanol on the surface of the specimen retards rot/decay (and the beetles appear to love a little booze with their meal). I was advised that meaty skulls and specimens are great for growing colonies, and my observations have confirmed this advice.

A pre-colony freeze is standard operating procedure for adding any dead wildlife to the dermestids. The freezing process is a little more complex than just thaw and add - one should partially thaw specimens and then refreeze. I playfully call this "shock and thaw" - any eggs/larvae that were able to survive the initial freeze are shocked and killed during Freeze 2 as they are emerging from dormancy.

Specimens that the beetles have successfully prepped from whole (eviscerated for entire specimens) include:
Adult Grey Wolf (skull)
Adult Black Bear (skull)
Adult Cougar (skull)
Adult Wolverine (skull)
Red-tailed Hawk (2, whole)
Great Horned Owl (whole)
Great Grey Owl (whole)
Northern Goshawk (whole)
Several small sparrows, flickers, warblers, grouse.

In their natural setting, flies (and their resulting maggots) out-compete dermestids. When dermestids are the only scavenger in the ring, they readily consume fresh and dried material. Actually, I have to time the addition of new skulls properly, because if I add fresh material to the same colony as a half-prepped dry specimen, the beetles will focus their efforts on the fresh skull. This was an pleasant surprising observation, given the myriad of "thou shalt not add fresh material!" lines of instructions on setting up/maintaining colonies. For large skulls I prefer to hang them just long enough to stop dripping - this cuts down on the chance that molds will grow in the colonies.

Also, while it is also common knowledge that the tongue, eyes, and brains need to be removed prior to adding skulls to the colonies, these are, without fail, the first parts of the skull that the beetles tackle. This is the stage that freaks visitors out the most - most people are not comfortable with seeing larvae and adult beetles wriggling around an eye socket or a mouth. It must invoke memories of horror movies.

I have not had any adverse reactions to using dried pet kibble in the colonies. My observations have shown that cat food is preferred over dog food, and I use the ends of the bags that my cat gets tired of. Actually, I've added several new batches of dermestids from infested pet kibble bags. Most people end up returning those to the store, but when you deal in beetles, it's a bonus!

Seeing as how I am not prepping skulls commercially (there is no "fast enough" for this experiment), I am willing to be patient as my colonies grow, and to not overgrow for the size of our facility. I have no timeline to keep. These colonies are for our small (but growing!) osteology collection, and for introducing kids to part of Nature's garbage crew. Kids are the one exception to the beetles in eye sockets observation - they think its simultaneously gross and, to quote one kid, "freaky-cool!" One day I aspire to have a large-museum set up for the colonies - where, as I've heard for one large museum, you can stick a whole fresh chicken in the dermestid colony and have it processed in three days - but I am purposely keeping the colony at a size that is manageable for this facility.

This was an issue of lids not being secure enough, coupled with a lot of open doors due to our renovation. 


  1. You aren't preping your skulls properly. Your supposed to remove as much of the flesh as you can. Make sure there is no "brains, tongue or eyes" and then freezing. You need to freeze them to remove and kill any potential pests, such as flies. Then make sure you dry it out nice, or it gets really nasty.

    Also your colonies are no where near the numbers needed to do any skull fast enough, and the longer the skull is in the setup the more risk to your Colony, flies invade, and all sorts of other critters [Red legged ham beetles] Your colony needs to be in the Thousands to really do anything quick enough.

    Hope this helps a bit, in the future I'd recomend growing your Colony a lot more. Also the pet food may/probably will cause Mites. Mites kill colonies!