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Tuna!
Join Date: Jan 2001
Location: PRE, Oregon
Posts: 1,279
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Cleaning skulls and dermestid beetles
For those who might be interested, I thought I would explain a little bit about how to go about using beetles to clean skulls. It is very very very easy process shouldn't be that expensive. Supposing that you have the room to do it (ie not in your apartment) it's a clean and relatively odorless process.
First get some dermestid beetles. This is easy. In most areas dermestid beetles are common and easily found by checking a few carcasses of roadkill or other carrion. A single gravid female can start a colony, but obviously the more that can be found to start with the faster the population will grow and the faster they will clean skeletons. Our local species, Dermestes maculatus, is common, easy to find, and most importantly does well in year-round captivity eating flesh and connective tissue. What you want to get started are the larvae. They look like little hairy worms. Doesn't take many to get a colony started. Make sure that you get it off of a mammal too if you are going to use them for a mammal and preferably the same type of mammal. They tend not to be species specific, but definitely different "strains" have preferences. Dermestid’s work well because they cannot fly at temperatures below approximately 80ºF, but reproduce and thrive at room temperature. Since they can’t fly at room temperature it is much easier to work with the colonies, putting in carcasses, taking out skeletons, etc. Keep them somewhere where it won’t get too hot or too cold. A garage is a good bet.
Next you need somewhere to put them and your skull. Any type of container that they cannot crawl out of or chew through will work. An aquarium will often work if you can get the antlers to fit. This is a great method for bears. My only caution is that the aquarium must be modified to hold bugs by trimming the silicon cement away on the inside corners so that they can’t climb out, but then the aquarium will never again hold water. Another option is a plywood box lined with epoxy resin. This box is designed to fit long bones and antlered skulls inside. It is also very hard and prevents the bugs from boring out through the bottom or sides as in ordinary wooden boxes. A lid is necessary because the lid keeps other insects out. There are many other species attracted to the smell of carrion which might cause problems. Maggots for instance, stain skulls. Also, ventilation is very important to the health of the colony. A dermestid colony needs a large, unrestricted exchange of fresh air.
When starting a colony you will need to provide a substrate for the bugs. I’ve used cut up egg cartons. Others use puppy chow, gravy train, or mighty dog brand dog food. No matter what you use, it will quickly becomes covered and mixed with an ever growing layer of duff. The bugs need water and prefer it daily, although they can survive several days without water, especially if the humidity is over 50%. A little bowl filled with cotton balls and soaked with water is a good option to keep your colony from drowning. You should also note that bug dust is hypo-allergenic and people with asthma, bronchitis or allergies should avoid working with the colonies. Try not to stir up the duff.
To initially prepare your skull, Skin the animal and remove as much soft tissue as possible. You don’t have to get everything, the bugs will get the rest, but the more you remove, the quicker it will get done. Cover your skull in paper towels, dampen with a spray bottle, and replace as necessary. It is very important to keep the substrate dry but the paper towels and specimens wet. You have the option of feeding specimens to the bugs in either a fresh or dried state but the beetles definitely prefer fresh meat and will go through it much faster if it is kept fresh and wet. Depending upon the size of your colony and the amount of material needed to clean off the skull, you can expect the process to take up to several weeks.
When all of the flesh has been eaten by the bugs the specimen is ready for removal. In order to prevent bugs from escaping into your house, the specimen must be fumigated to kill any bugs that may be hiding inside the bones. This can be done in several ways:
Immersion in hot water. This is excellent for small specimens and birds in particular but on large specimens the bones may crack if the water is too hot. Hot tap water is hot enough to kill the adults and larvae, is very quick and very safe. On large mammals it may crack the teeth if extremely hot water is used.
Immersion in Ammonium Hydroxide. This is even better than hot water but requires a really good fume hood.
Freezing. By placing the specimens in a house-hold type freezer at —18ºC to —20ºC for 72 hours all bugs should be killed. Large mammal skulls should not be frozen because this may also crack the teeth.
Hot water is a good bet, because it streamlines the process of cleaning specimens by not only killing the bugs, but also rinsing off any duff clinging to the bones. After killing the bugs the skeleton should be soaked in water for several hours to rehydrate any tissue that the bugs might have missed. Soaking makes such tissue swell and makes it easy to see and scrape away anything left with a scalpel or knife of appropriate size. Absolutely all flesh and connective tissue must be removed from the bones.
Use fine tweezers to remove any dead bugs and larvae from inside the skull, auditory bullae, vertebrae and other small openings. One advantage of killing bugs with hot water rather than with freezing or ammonia is that more bugs actually escape from the skeleton making it easier to clean. This can save a tremendous amount of time.
Some people don’t care to have their specimens degreased, others do. If you want to remove the oils from the bone there are several options.
In a museum setting, Ammonium hydroxide is often the tool of choice. It does not bleach the bone and change its natural color, but does a good job of removing the oils. It will decalcify the bone, so bones cannot be left in it for long periods. The main drawback however is that you the need a fumehood. It can be unpleasant and even dangerous without the proper equipment to clear its fumes.
Hydrogen Peroxide. Can be used to degrease and also bleach the bones. It will make them a very bright white and remove all of the oil, but will also decalcify them if soaked too long. Peroxide has the advantage of being readily available to the non-museum user and also being user friendly with absolutely medicinal qualities.
The third, and my preferred option, is Diaper soap. A mild soap, not a detergent with perfume or other additives, can be used to simmer the skeletons and remove the fats and oils. This has the disadvantage of being labor intensive. However, when you are working on a single specimens and you don’t want to bleach the skeleton, this works very very well. Soak the specimen and lightly scrub it with a brush to wash away all the grease and any duff from the beetles. Let dry and you are done.
Hope this helps, any further questions feel free to post here or e-mail me.
[ 11-17-2003, 06:07 PM: Message edited by: birdhunter ]
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