How to beetle-clean bones

How many beetles do I need?

Dermestid beetle colonies keep growing in size. With some patience, your starter colony will eventually grow to the size of a professional cleaning crew.

At least 300 beetles would be necessary to start cleaning a skull the size of a rodent or bird. After a few weeks, their numbers will have grown to a minimum of 1000 beetles and they should be able to consume a deer skull. If you are cleaning volumes like a small business, you may require 5000 beetles or more.

7,5 grams = ~150 beetles

15 grams = ~300 beetles

50 grams = ~1000 beetles

Preventing mass death

Salinity (and saltwater fish):

Keep the salinity of the food in mind. Bacon can be deadly since it is high in salt. Dermestes frischii is relatively tolerant of salt. They can survive a salt content of 25%, whereas the mortality of Dermestes maculatus is 100% with a salt content of 9.2%. Dermestes ater is also adversely affected by salting. If you are planning on cleaning a saltwater fish, then the species Dermestes frischii is highly recommended.

Antiparasitic drugs (in pets):

To keep your beetle colony save, the first question to ask before agreeing to clean the bones of a pet is if the pet had recently had any antiparasitic drugs. This kind of medication is very deadly to beetles as well. If there is a chance that the drugs are still active within the body, you might kill your whole beetle colony if you feed it to them.

Predatory beetles:

A dermestid beetle colony can be infested by predatory beetles. Red-legged ham beetles (Necrobia rufipes) and buffalo beetles (Alphitobius diaperinus) are examples of beetle species that can kill your dermestid beetle colony slowly. They actively target smaller larvae and damage eggs and pupae as well. When your beetles are predated, you'll eventually be left with adults only and no new offspring seems to appear. Predatory beetles can go unnoticed for quite some time, since species as the buffalo beetle likes to hide within the styrofoam.

You might be able to save your dermestid beetle colony, by removing all predatory beetles. Sometimes this means to handpick your dermestid beetles out of the enclosure and provide them a new one, since the eggs of the predatory beetles can be present anywhere in the bedding.

Mites:

Another pest that can infest your dermestid beetle colony are mites. Mites flourish when the bedding of the enclosure is moist and they can cause harm if they are present in big numbers. In nature, mites will use insects like beetles to bring them from one food source to the other. When mites cover an adult beetle or a larvae, they tend to stay in crests, such in between the segments of the body or at the joint of legs. If there are many mites on a single individual, the movement of the beetle will be hindered so much that the individual eventually won't be able to walk to or eat the food. The individuals that are covered with mites will slowly starve to death.

Mites need the humidity to be higher than 50% RH to survive. The minimum RH differs per species, but they can all survive with a humidity lower than 50%. Lowering the humidity can be an effective way to get rid of mites. Be careful with ant-mite treatments, because all strips and sprays will kill dermestid beetles as well.

Preparing the food for the purpose of skulls and skeletons

You can't simply put a whole animal in the beetle enclosure and expect good result. There goes effort into preparing the food for your beetles if you want to clean the skull or the whole skeleton in a pleasant manner. The following steps describe how to be the best chef for your beetles, so they can clean the bones with the highest quality they can offer.

Step 1: Skin the animal

Dermestes species won't eat the scales, feathers or coat of the animal. There are other dermestid beetle (Family: Dermestidae) species that do eat fur, for example the carpet beetles (Anthrenus spp.) such as the museum beetle (Anthrenus museorum). However, the adult carpet beetles feed on nectar and need certain flowers to reproduce, making this genus difficult to cultivate. Back to Dermestes, all you can expect of your beetles, is that they at most make holes in the skin to get to the meat. All feathers or hair of the animals will eventually scatter throughout the bedding of your enclosure creating a mess and pieces of dried skin will remain. The first important step is to skin the animal that you'll feed to your beetles. This is easy to do with a scalpel.

Step 2: Remove the organs

If you don't remove the organs, you will end up with pieces of dried organs. Especially if you clean the skeletons of herbivorous animals, your beetles will most definitely not eat the contents that are present in the stomach and intestines. The poop will end up somewhere in the enclosure. The organs are the most stinky of the whole cadaver and are the first parts to start rotting, so for your own nose you really might want to remove them. The eyes are also organs that you will have to remove from the skull. The brain is another organ with a very prominent smell. In small animals, like rodents and birds, it's not necessary to remove the brain. The fats that are present may actually boost the breeding of the beetles. With bigger skulls, try to remove as much brain as possible. Beetles will get stuck and drown in the brain tissue that eventually liquefies.

Step 3: Divide the body into pieces

This step is perhaps not mandatory, but I think it really helps to really thoroughly clean a skeleton. I remove the skull first, so that the beetles are able to access the brain cavity through the foramen magnum. After that, I remove all libs. The front legs are detached by cutting underneath the schoulder blade towards the front of the animal, until you can seperate the clavicle from the sternum. In some animals, like cats, the clavicle isn't attached to the sternum so the bones of their front legs aren't connected to the rest of their skeleton. The hind legs are detached by getting the joints of the femurs out of the hips. Like this, you won't damage the bones of the skeleton in any way and you can feed the different parts to your beetles separately. It's also possible to pull one of the parts out of the beetle enclosure more early than another part. It's not surprising if they eat a paw much quicker than the chest. If you collect the cleaned leg from the enclosure, the beetles can proceed with cleaning the chest and you don't have to worry that the beetles will start to destroy the more fragile legs.

Step 4: Dry the meat

Moist meat will start to rot if your beetles can't clean it in a timely manner. Besides that, some sort of residue is often left on skulls and whole skeletons tend to fall apart completely when fed to the beetles without drying it first. It is possible to air dry the meat, but keep flies away. Maggots secrete enzymes that keeps the meat moist. Using a food dehydrator definitely does the trick.

What to do when the beetles are finished?

Directly after the beetles: Try to remove as many beetles as possible. If a small larva dies during the cleaning process in a spot where it's hard to remove, you'll be bummed that you didn't urged it to leave the spot while it was still alive. Clean the beetle poop of your bones by soaking them in water.

Removing grease: There might still be grease present inside the bones. This can present itself as yellow to translucent bone that sometimes feel sticky to the touch. Soaking the bones in acetone can help to remove fats by dissolving them. Eventually, the acetone will end up yellow when a lot of fat is dissolved in it. However, acetone is only able to remove the superficial fats. If you're cleaning some big skulls or bones, you can only remove the deep-seated greace by long-term soaking in warm water mixed with dish soap.

Whitening: If you want to whiten the bone, use hydrogen peroxide. Some people already experience good results with 9% and I personally prefer to use 12%, those percentages aren't strong enough to cause any damage to bones. Hydrogen peroxide (H2O2) oxidizes, so oxygen (O2) is released during the process. That's why active hydrogen peroxide creates a lot of bubbles. Eventually, the hydrogen peroxide loses it's effectiveness, since only water (H2O) will be left after this reaction.

Building the skeleton: If the parts of the skeleton, such as the ribcage, are in a different position than desired, you can slightly wet the bones with water to carefully reposition the bones. Cartilage will break easily, but become flexible when wet. When you are glueing pieces together or teeth back in the skull, you might want to use wood glue. It's easy to remove excess glue and if you accidentally glued something wrong, you can simply soak it in water to undo your mistake. However, wood glue isn't very strong and non-supported parts of the skeletons might slowly start to droop over time. Bigger skeletons require metal rods to support the joints against gravity and smaller skeletons can be fixed into position with a tiny dot of super glue. Be carefull with super glue, since excess glue will remain visible and any mistakes will be more permanent.

Bibliography:

  • Magni, P.A., Voss, S.C., Testi, R., Borrini, M. & Dadour, I.R. (2015). A Biological and Procedural Review of Forensically Significant Dermestes Species (Coleoptera: Dermestidae). Journal of Medical Entomology 52(5): 755-769.