Building a Chest Freezer Dermestarium

This was my first Dermestarium build and the unit I used for almost 3 years. These pictures and the write up were done in 2016. There are other ways to build them, and cheaper ways, but I built this one with safety in mind, and I also used a working brand new chest freezer because I wanted it to look nice and clean, be able to cool, not just heat, and also a good friend worked at an appliance store and I got the freezer for cheap.

I’m not suggesting this is the best way, or the only way, it is simply the way I chose to build mine utilizing what I know about reptile caging as far as temperature control, ventilation, and safety (lowered fire risk) in mind. Take this as an example and not an exact how to. You can get creative and use different parts. The basic concept is the important part.


I started with a new freezer. You certainly don’t have to, but I have a friend that works at an appliance store and this 10.2 cubic foot Insignia only cost me $137, so why not? It’s clean and new, and it works. I wanted to be able to not only warm the beetles, but cool them as well. I set the heat to 78F, and the cooler to 82F so that it maintains an average of 80F using the Inkbird thermostat.

I ordered all needed new parts from Amazon, and collected all parts before beginning my build.

I used a 2 gang wall plate for household outlets for the thermostat and humidistat. The plate ALMOST fit them perfectly, but I did have to take a file and widen the openings just a smidge.

I removed the stock thermostat and, since they went with a funky shape on this model of freezer, I then took a saw to the hole to make it fit the new thermostat and humidistat.

I then wired the thermostat up to the compressor and heat panel. Instead of going into that here, just google “wiring stc-100 chest freezer” and check out the plethora of pages with instructions on this. There are also videos.

Next I installed the louvered vents. I accomplished this using a 1″ hole saw with a center bit. I like to keep things looking professional, as if it were built this way at the factory, so I started on bottom and centered the bit in one of the dimples this model of freezer has and went SLOWLY through the plastic to avoid cracking it. I went far enough up to let the center bit of the hole saw go through the top, but not the 1″ part. I then closed the lid and slid the bit into the new hole and finished the cut from the top. I then vacuumed the mess up and installed the vents. They simply push in and stay nice and tight.

I then used the 1″ hole saw again and drilled a hole in the “hump” of the freezer. From this hole is where the vacuum hose will drawal air to vent the dermestarium.

I chose the hump because the outer walls of chest freezers are lined with coolant lines and there is no good way I’m aware of to locate these lines and avoid them. Cutting one would cause the coolant to leak everywhere.

I installed a louvered vent on the inside only.

Next I installed the radiant heat panel. I used self tapping screws to mount it on the bottom, or inside, of the freezer door. Go slow and let the self tapping screws do the work, or predrill, to avoid cracking the plastic.

After that I used a 3/8″ drill bit and drilled a hole directly behind the heat panel, and another hole on the back edge of the freezer door. I then used a wire hanger to ream out the hole and clear the insulation out of the way. I removed the plug end of the heat panels wire because it is not used in this application and is wired directly to the thermostat. I taped the wire to the hanger and pulled it through the hole. I then installed a 3/8″ rubber grommet in both holes to seal it off and give it a finished look.

After that I took a 2″ hole saw and cut through this little vent plate on the back of the freezer to allow the vacuum hose to slide through.

I removed the side panel of the freezer for easier access and then ran the hose through the hole I cut in the vent plate. This model of vacuum I found at Goodwill had a perfect elbow bracket with screw holes for mounting it. I utilized this and double sided tape to mount the hose over the vented hole I cut from the inside and to seal it so it could only drawal air from that hole. Once again I used self tapping screws.

After that, inside the hump of the freezer I accessed by removing the side panel, I drilled a small 3/8″ hole towards the front, opposite side of the vent hole, and ran the temperature probe for the thermostat, and the humidistat probe through the hole.

I then used window screen pieces and positioned them at random angles to create even smaller holes and cut them into a square. Then I neatly tucked up the probes and used aluminum ducting tape around the screen creating a beetle proof cover over the probes. Then I shot some spray foam insulation into the hole, just enough for a good seal.

Next I used aluminum ducting tape over every seam, on the hump, and at two different levels of height around the inside of the freezer. The beetles cannot climb over this tape and will simply fall off if they try. This is just a precaution.

I completely forgot to take pics of the window vent process, but it’s fairly straight forward. I positioned my freezer in front of a window so I can vent it to the outdoors.

To accomplish this I used a piece of MDF board, cut it to the right width and height (8 inches tall and 34 inches wide in my case, yours will probably be different) to fit in the window. I painted it black, lined it on all sides with foam insulation tape, cut a 4″ hole in the center, placed the computer fan over the hole, the fan shroud to 4″ hose opening over the fan, and screwed them onto the wood. Make sure the fan is aimed to blow out the window. I then put the hose reducer on the shroud so it will accept a standard vacuum hose instead of a 4 inch hose.

After that I simply opened the window, slid the board in, closed the window on the board, stuck the hose I installed in the freezer into the reducer hooked to the fan on the window board, and plugged the fan in. This successfully created a nice constant negative pressure inside the dermestarium by slowly pulling air through the vents on the lid, and pushing it out of the window.

Now the freezer is finished and ready for use. It can be used like this as is, with bedding in the bottom, but I chose to use a rubbermaid container I found at Wal-Mart that fit great in the large bottom area. I did this to allow for easier future maintenance and cleaning. I can simply pull the beetles out.

I used the hanging basket that came with the freezer to place finished skulls in to hang and allow hidden beetles time to escape and simply fall back into the main colony.

I no longer use this setup, however it did work excellent for several years and there’s no real reason I couldn’t have continued to use it. I simply evolved my methods and knew I needed a different setup to work more efficiently on the types of animals I mostly deal with, which is reptiles and birds. So I designed a dermestarium inside of a commerical double door cooler that contained a drying rack, and hanging rack to get the beetles off of freshly beetled bones, and a colony in the bottom. I’m working on a write up for that one next. Admittedly it is overkill for most people.

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